We had some trouble with this this week. My kids each had a separate ecard as a gift from their aunt. My son spent some of his at Disney Springs building his own light saber, and had a balance. My daughter went to use hers in Germany and her balance was the same as what my son's leftover balance was. It was like they were pulling from the same pot of money. They were each $25, so we should have gotten $50 worth, but we only ended up getting $25 worth total. I still can't figure that out. My sister in law said her credit card was definitely charged $50.
Now, they also each had $25 egift cards that they spent with no problem.