LRW Curves and distributions

[victortsoi]

I'm trying to wrap my head around how LRW is curved. Lets say a schools handbook says something to the effect of "faculty are requested, where possible, to conform their grades to the following:
5-10% A, etc, 5-10% C+ or below..."

LRW is supposed to have a mean gpa of around 3.1-3.33.

Does this mean that someone *must* get a C+ in any given LRW class? Or can the lowest grade be a B-?. I am a little lost on how exactly these curves are applied

[HiiPower2015]

I would assume that it depends on your school's policy. I know at my school the policy is that the professor can apply the curve if he wants to. It is my understanding that most professors use the curve, but are able to use their own discretion in bumping up the C+ grades to a B- under their discretion