They scratch off, not peel off. Put it back in place and use a penny (or other coin) to gently scrape off the silver. I received a steam gift card from Best Buy for Christmas and I accidentally scratched off some of the numbers on the 15 digit code.
Use the Gift Card Troubleshooter Your notifications are currently off and you won't receive subscription updates. To turn them on, go to Notifications preferences on your Profile page. Pinned. Unpinned. Unable to pin.