You can also refund the credit to the customer by entering REFUND in the Apply-to field. When you do this, the system first uses the credit to pay off any remaining balance on the subscription and then refunds the balance to the customer (if the subscription is fully paid, the entire credit amount will be refunded).
In these refund scenarios, the order recap display that is shown at transaction wrap-up now also displays the amount being refunded to the customer - as a separate field.
Note that this is the expected refund amount, at the time that the transaction occurs. Other subsequent actions within the system could affect the ultimate amount refunded.