Credit memo receipt

Hi, yesterday I made a purchase from the apple store with delivery express, but the guy never came or called and later an email said that the items were sent back to the store and that they would do a refund; but today I received a credit memo receipt and I don't understand exactly how to use it or if it's just a receipt that they already send the money to the bank.

I would really appreciate if someone can help me out. I'm just traveling in the USA and I'm going back to my country next week.