It says 10-22pF, so pick 15pF as a starter... kinda midway...

It's not a critical PIC, hell, it'll work from a piece of wet string in RC mode. Anything will get this going... 4Mhz Ceramic resonator, whatever... remember it's a replacement for the 16F87x when you run out of steam... you drop this PIC in it's place, and as long as you didn't have a flaky design to start with, away you go...