Amount exceeds refundable

422 · https://docs.rostergiving.com/errors/amount-exceeds-refundable

POST /v1/refunds asked for more than what is left to refund on the donation, or nothing is left. No refund was created.

What is left is the donation's amount minus its refunds that have not failed or been canceled: a refund holds its amount from the moment it is created, not only once it succeeds. Read the donation's refunds with GET /v1/refunds?donation_id=…, add up the amount_minor of those that are not failed or canceled, and send at most the difference, or omit amount_minor to refund what is left. See Partial and multiple refunds.