Mark's got the summary, but the long version of it is that it depends on profession, the type of list, and the level of spells you are trying to learn on that list. For example, a pure caster (such as a magician), wants to begin learning Light Law, one of his base lists. He spends DP points to learn ranks in that list, which will be added to his spell gain roll. Since he's a pure, learning one of his base lists, he gets an "B" type pick, which means all spells from levels 1 thru 10 will be learned, once he makes a successful spell gain roll.