Victoria's Secret "Secret Reward" Card?

I have two of these cards as I have hit two VS over the weekend looking for various sizes of Pink hooded sweatshirts for holiday gifts. The thing is, I don't like how they say that you can discover the balance when you make a purchase (between Dec 1-24). I mean, I don't want to get up to the register and find out it only has 10.00 on each one which is likely, and they expire so soon! Does anyone know how to find out how much is on each card? Is it a really that big of a secret? I know there must be some sort of code.