HQ · Horizon Quantum Holdings Ltd.

Each stock option is exercisable for 2.43499 Class A Ordinary Shares of Horizon Quantum Holdings Ltd. (the "Company") at a price per share of $5.13.

Stock options received as part of the business combination (the "Business Combination") contemplated by the Business Combination Agreement, dated as of September 9, 2025 (the "BCA"), by and among Horizon Quantum Computing Pte. Ltd. ("Legacy Horizon"), dMY Squared Technology Group, Inc., the Company and certain other parties, as described in the Registration Statement on Form F-4, as amended and supplemented (File No. 333-292737), initially filed with the U.S. Securities and Exchange Commission on January 14, 2026, and declared effective on February 17, 2026. Upon the closing of the Business Combination on March 19, 2026, Mr. Gould's stock options exercisable for Legacy Horizon ordinary shares awarded by Legacy Horizon were exchanged for substitute stock option awards of the Company of an equivalent economic value, which are subject to a vesting schedule as further detailed in footnote 3.

Pursuant to the BCA and as a result of the closing of the Business Combination, Mr. Gould's 285,300 Legacy Horizon stock options were exchanged for 285,300 stock options of the Company of an equivalent economic value, with an exercise price per Class A Ordinary Share of $5.13.

The stock options held by Mr. Gould are subject to Mr. Gould's continued employment with the Company and vest quarterly in 16 equal installments, beginning on August 15, 2025. As of March 24, 2026, 35,662 stock options are fully vested and exercisable, with the remaining 249,638 stock options vesting in accordance with the forgoing schedule.

Each stock option is exercisable for 2.43499 Class A Ordinary Shares of Horizon Quantum Holdings Ltd. (the "Company") at a price per share of $0.15.

Stock options received as part of the business combination (the "Business Combination") contemplated by the Business Combination Agreement, dated as of September 9, 2025 (the "BCA"), by and among Horizon Quantum Computing Pte. Ltd. ("Legacy Horizon"), dMY Squared Technology Group, Inc., the Company and certain other parties, as described in the Registration Statement on Form F-4, as amended and supplemented (File No. 333-292737), initially filed with the U.S. Securities and Exchange Commission on January 14, 2026, and declared effective on February 17, 2026. Upon the closing of the Business Combination on March 19, 2026, Dr. Tan's stock options exercisable for Legacy Horizon ordinary shares awarded by Legacy Horizon were exchanged for substitute stock option awards of the Company of an equivalent economic value.

Pursuant to the BCA and as a result of the closing of the Business Combination, Dr. Tan's 500,000 Legacy Horizon stock options were exchanged for 500,000 stock options of the Company of an equivalent economic value, with an exercise price per Class A Ordinary Share of $0.15.

The stock options held by Dr. Tan are fully vested and exercisable.

Each Class B ordinary share, with no par value (the "Class B Ordinary Shares"), is convertible, at any time, in exchange for one Class A ordinary share, with no par value (the "Class A Ordinary Shares").

Class B Ordinary Shares, received on March 19, 2026, upon the closing of business combination (the "Business Combination") contemplated by the Business Combination Agreement, dated as of September 9, 2025 (the "BCA"), by and among Horizon Quantum Computing Pte. Ltd. ("Legacy Horizon"), dMY Squared Technology Group, Inc., Horizon Quantum Holdings Ltd. (the "Company") and certain other parties, as described in the Registration Statement on Form F-4, as amended and supplemented (File No. 333-292737), initially filed with the U.S. Securities and Exchange Commission on January 14, 2026, and declared effective on February 17, 2026.

Pursuant to the BCA and as a result of the Business Combination, Dr. Fitzsimons exchanged his then outstanding 8,108,696 ordinary shares of Legacy Horizon for 19,744,585 Class B Ordinary Shares of the Company.

On March 6, 2026, dMY Squared Technology Group, Inc. ("dMY"), the Company, and Horizon Quantum Computing Pte. Ltd. entered into a subscription agreement with Penchant Family Holdings LLC, whereby the Company, upon the closing of the Company's business combination with dMY, would issue 84,602 shares of the Company's Class A ordinary shares, with no par value (the "Class A Ordinary Shares") to Penchant Family Holdings LLC at a price per share of $11.82, for an aggregate purchase price of approximately $1,000,000. The closing of the Company's business combination occurred on March 19, 2026, and the 84,602 Class A Ordinary Shares of the Company were sold to Penchant Family Holdings LLC on that date.

Penchant Family Holdings LLC is controlled by Penchant Holdings, Inc., its Managing Member, of which Danielle Lambert serves as its President.

In connection with the closing of the business combination (the "Business Combination") among Horizon Quantum Holdings Ltd. (the "Issuer"), Horizon Quantum Computing Pte. Ltd. ("Horizon"), and dMY Squared Technology Group, Inc. ("DMY"), these Class A ordinary shares of the Issuer were issued pursuant to the terms of the Business Combination Agreement, dated as of September 9, 2025, by and among the Issuer, Horizon, and DMY (the "Business Combination Agreement") upon the exchange of 1,163,484 shares of Class A common stock of DMY. On the effective date of the Business Combination, the closing price of DMY's Class A common stock was $13.50.

dMY Squared Sponsor, LLC (the "Sponsor") Sponsor is the record holder of the securities reported herein. Harry L. You is the managing member of the Sponsor and has voting and investment discretion with respect to the securities held of record by the Sponsor. Each of the Sponsor and Mr. You is a "Reporting Person" and may be deemed to beneficially own the securities reported herein; however, each Reporting Person disclaims beneficial ownership of the securities reported herein, except to the extent of such Reporting Person's pecuniary interest therein. Solely for purposes of Section 16 of the Exchange Act, each Reporting Person may be deemed a "director by deputization".

In connection with the closing of the Business Combination, these warrants of the Issuer were issued pursuant to the terms of the Business Combination Agreement upon the exchange of 2,884,660 warrants of DMY. On the effective date of the Business Combination, the closing price of DMY's warrants was $2.69.

dMY Squared Sponsor, LLC (the "Sponsor") Sponsor is the record holder of the securities reported herein. Harry L. You is the managing member of the Sponsor and has voting and investment discretion with respect to the securities held of record by the Sponsor. Each of the Sponsor and Mr. You is a "Reporting Person" and may be deemed to beneficially own the securities reported herein; however, each Reporting Person disclaims beneficial ownership of the securities reported herein, except to the extent of such Reporting Person's pecuniary interest therein. Solely for purposes of Section 16 of the Exchange Act, each Reporting Person may be deemed a "director by deputization".