I'm new to Adventure paths but curious about the world they are set in, we just destroyed the Cheliax Dominator in book 2, during the fight I was surprised that the GM said ships like that typically carry 24 spell casters capable of detecting invisibility (I tried to do some invisible stealth recon). Is there some source book that discusses what a ships compliment typically is, or for that matter what ratio of population is spell casters in general?