I think what we're seeing with the bracer's "confusion" is the conflict between predictamancy and mathamancy, the fact that they cannot overlap, and the debate of Fate/Natural Predictamancy. The Bracer, being Mathamancy, was capable of calculating Parson's odds of casting, but it couldn't account for events of Fate. So the number shown first was it's real result, and the switch to zero was just natural predictamancy kicking in and overriding the bracer's magic.
I like the sounds of this explanation. Basically the bracer was saying "you have a 99% chance to cast the spell, but if you try, there is a 99% chance that something (like the falling rocks) will stop you from succeeding." This would mean no one is actually messing with the bracer, not even the 'summon perfect warlord', but rather that the question has two answers, and the bracer is trying to display them both. Goes to show just how powerful the bracer is.
@oslecamo2_temp I don't think it is odd that Charlie wants him out of the picture. Whatever plans Charlie has/had in motion, it's obvious that Parson is messing with them, and getting him out of Erfworld is an easy (because Parson wants it) way to accomplish that, at least in Charlie's mind.