the seller write so much and say that please confirm

Hi I recently buy a Amazon gift card and redeem this on my account, the seller write so much and say that please confirm, but I don’t sure if do that because since few hours I and my brother buy two of them and my brother claimed his gift card and confirm, next to it refresh the page and the balance is in 0$ he can’t do anything because he confirmed the product. And this was the start of the history next to it the same seller send my the same code that was exactly the same that my brother use, I obviously say that is blocked and he refund my money but my brother was scammed. And now I don’t Kwon what to do…
Can I wait the 3 days to confirm ?
Can the seller claim his Amazon gift card if I already use it?
Please help, I only buy some things in this page D:

Hello!

Yes, you can wait 3 days to complete the sale (or the system will complete it to you automatically).

Can the seller claim his Amazon gift card if I already use it?
I don’t think so, but only Amazon can you confirm this to you, so i suggest confirming with their support.

Also, if your brother were scammed somehow, please, ask him to send a support ticket to our team and send all the proof he has so we can investigate this further.

https://gameflip.zendesk.com/hc/en-us/requests/new

Thank you.