above "C" rank aswan potentials

I'm pretty sure he's saying, you use circulator, it chooses the rank, then chooses the effect.

I used a rank 9, well a few, and stopped myself at a Rank S ability, that gives 39% buff time. Just didn't have enough to bother going further, and can deal with extra buff time for now.

Only you don't stay on a specific rank once you recirculate, so it make so sense saying you get your rank and then can get anything from that pool.
Or, does each of the circulators have their own pool of options?