Staggering Critical "Stacking"

[standaloneghost]

Per the text of Staggering Critical -

Quote:

Benefit: Whenever you score a critical hit, your opponent becomes staggered for 1d4+1 rounds. A successful Fortitude save reduces the duration to 1 round. The DC of this Fortitude save is equal to 10 + your base attack bonus. The effects of this feat do not stack. Additional hits instead add to the duration.

What exactly does it not stack with? It seems like the text in this context the last two sentences directly contradict each other. Do multiple Staggering Criticals mean multiple rounds of stagger, either for 1 or 1d4+1 rounds depending on save?

[wraithstrike]

It is saying you don't get to keep adding 1d4+1 rounds to the duration. Instead 1 round is added to the duration.

[Saethori]

By not stacking, I'm pretty sure that is meant to refer to the notion of having two simultaneous Stagger conditions going on, and it wants to ensure you only are staggered once at a time.

Nothing written in the ability implies you only add one round to the duration if they already have it. It says you add to the (existing) duration, from context in lieu of stacking. Which means they make an additional Fortitude save to determine whether you're adding 1 round, or 1d4+1 rounds, to their existing stagger.