How do credit card refunds work if you've already paid the bill?

say that your credit card bill is $20 and you pay it off. You then have to get a refund for a product that was $10. Since you've already paid the credit card off in full, where does that $10 refund go?|||It goes into your account as a credit. It first gets used to pay for anything you buy before the next months cycle and if there's anything left at the end of the cycle it is shown as a credit to be used the following month. If you closed the account and it had a credit you would get a check for that amount.|||A credit for nxt months bill