After signing in to the Microsoft for Startups Founders Hub, navigate to the 'Benefits' tab and click 'Redeem' under the Azure Sponsorship benefits section. When redeeming credits, please ensure you use the email address associated with your Azure subscription.
Refer to the following doc, Applying Azure Credits
If credits have been applied to the incorrect Azure subscription—or if you'd like to transfer them to a different subscription (such as Subscription 1 in your case)—these situations are not directly addressed in the documentation. However, the recommended approach is to escalate such cases to Azure Support or the Azure Subscription Team for assistance.
To resolve your issue:
Contact Azure Support or the Subscription Team.
Clearly explain the situation, including that the Azure startup credits were applied to a new subscription but need to be transferred to a different one.
For additional support, you may also consider submitting a ticket through the official Microsoft for Startups support channels.
If the information is helpful, please Accept Answer & Upvote so that it would be helpful to other community members.