• Full — refunds the whole refundable amount (order total minus any cancellation fee and minus what was already refunded) to the selected method. You are asked "Are you sure you want to REFUND ALL?".
• Custom — you type an Amount; it must be greater than 0 and, combined with earlier refunds to that method, may not exceed the order amount, otherwise you get "You can only refund X with the method selected!".

In both cases the order is cancelled afterwards.