[PF] fractional CR confusion

[humanallergy]

I'm a bit confused about adding class levels to creatures with fractional CR as they fit the no racial hit die descriptor as well.

According to the core book, I apply levels and then subtract one (two for NPC classes). Yet, the back of the bestiary doesn't seem to mesh with this. When adding class levels to a creature it says to give bonuses to its abilities and then consider its role in combat and add to CR based on that and racial hit dice.

With the lack of racial hit dice in fractional CR races, should I still apply these ability bonuses and then subtract one for the level to determine the final CR or just keep the abilities in the book and go from there.

I'm so confused!

[gr8artist]

This is really a problem that should only annoy you for the first few levels of a character's growth.
My suggestion: Give any creature with a fractional CR 1 NPC class level, in addition to its racial hit die, if any. Now call it a CR 1/2 or 1/3, which puts it in line with the races found in the bestiaries. (ie. Drow have a CR of 1/2, I think. the little elemental races have a CR of 1/3, I think.)
Now give it class levels as desired. Ta'Da!
But the xp difference between a CR 1/2 and a CR 1/3 is roughly equivalent to talking your way past a guard when you're out past curfew. Don't worry about it so much.