The percentages are used to tell a buyer what the chances are that babies are hets. Since the mother is albino, then all the normal looking babies she has are hets, so they are 100% hets.

And since you got albino babies from him last year, you know for sure he is a het, so he's 100% het.

Knowing he's a het, if you mated him to a normal wild-type female, the babies would all look normal but would have a 50% chance of being hets, so until each one was proven or unproven to be a het, the babies would be called 50% hets.

That's not the case though. The mother is albino, the father has already been proven to be a het. So, you have a 50/50 chance of producing albinos, but even if by chance all the babies came out normal looking, the babies would all be 100% het for albino. Any normal looking babies you get from those two would be 100% hets.

@ Marnie: Albino checkered garters are probably the least expensive albino garter snake you can buy. I've seen them for as little as $40.

Pastels on the other hand, are pretty darn expensive.