When you purchase a prepaid card bundle, the items are in the Gift Window the next time you log into the game.
Once you claim an item from the Gift Window, it is in your inventory and removed from the Gift Window. You can only claim an individual item once from the Gift Window. If you leave an item in the Gift Window to be claimed later, you will be able to choose the item you want when you redeem it.
Items from the prepaid cards do not 'grow' with the character you redeem it on. The item you chose when you redeemed it from the Gift Window is the item you get.
