Quote Originally Posted by JackPhoenix View Post
Then why are you sure removing the charm ability would lower creature's CR? I think it's much safer to assume that with a table that list creature features and how they influence creature's CR, the CR of the example creature in that very table would take the relevant ability into account. Why would presence or absence of Charm ability on a given creature influence the creature's CR if the table lists charm as an ability that does not impact the creature's CR?
The idea is for you not to double-count such an ability. You should have already factored it in under Step 12 ("Save DC Traits") before you got to Step 13 ("Special Traits, Actions and Reactions.") Charm is a zero under Step 13 because you were supposed to have accounted for it in Step 12 already.