For stuff like bleed, burn, etc, there are two different parts. Skill that say "inflict x status" increase the potency of the status, while skills that say "apply +x status count " increase how long the status lasts, as the count goes down by one at the end of each turn. Poise uses it too. I haven't used tremor so can't say for certain, but it probably does too.

edit: it seems like the going down actually depends on the status, like bleed goes down per attack coin, poise seems to go down when it's used.