I purchased too many returns.

I don't think you can/do.  BUT if so, you'd have to contact customer services.

THIS is a peer-to-peer "fellow users of the Intuit suite of software"  forum.

It's sort of like buying too many sliders at White Castle?

Here is the fine print from https://proconnect.intuit.com/tax-online/pricing/

For Tax Year 2019: All Intuit ProConnect Tax returns pre-ordered and purchased are for use during the calendar year 2020 and can be used for any tax return supported by Intuit ProConnect. 1040 and business returns and can only be used for the designed return type. Returns purchased but not used by December 31, 2021, will not roll over into the next tax year. Any pre-orders not canceled prior to December 31, 2020 will be charged to the credit card on file. Intuit has no obligation to refund all or part of the purchase price for prior purchases of ProConnect or unused returns. ProConnect tax returns are credited to the Customer Account Number that purchased them and cannot be transferred to other Intuit accounts. Terms, conditions, features, availability, pricing, fees, service and support options are subject to change without notice.