When you enter in the gift card at checkout for the first time, the system redeems it and puts the money in your SkyWallet in order to pay for the order. If you leave the checkout process after entering the gift card, the money is still in the SkyWallet. In order to use the funds from the gift card, at checkout you will choose the "Add Payment From Sky Wallet" button that is right next to the "Redeem Gift Card" button. Once you click on the button, you will be able to see the amounts you have in SkyWallet and add those to the order.