I actually type in the number in my Notes app so I can copy and paste instead of reading and transcribing the numbers each time. Mobile ordering for counter service, G+, and mobile payment in the bigger stores (like the World of Disney) all automatically charge your credit card on file instead of getting charged back to your room. There is a spot on the app that you can choose a different payment method but the app doesn't remember your gift card number so you need to enter it each time. A copy and paste saves me a few seconds which can be important for G+, even more when I have fat fingers trying to type in the gift card number. I use my MB (or Disney app or Apple watch) for everything else

.