Simply put, the percents mean the percent chance that the snake could be het for that trait. 100% chance of being het, 66% chance of being het, etc. So anything less than 100% is a gamble. You get the possible hets (66% or 50% and so on) when you cross hets together.

BTW for what it's worth, I just wrote an article on this stuff that'll be in the next Reptile Times issue... Comes out in 5 days, might help you out.

-Jen