I've not played with it.
But my understanding is that it will round-robin within the target group.
Which could be all your toons, or all toons within an ATG.

I would assume alphabetically, if in an ATG.
And probably by lower Slot number to higher Slot number, if using all your toons.

The reset to step 1...
Can be from the first press or from the most recent press.
And the do not advance would be the same.
Pretty sure these options would function identical to previous.

I should mess around with the feature a bit.
But pretty much, go with what I have.
Until I need to implement something new.
At which point, a new round-robin would take advantage of the new method; an existing round-robin would be one step per toon.