This preset processes up to 8 channels independently and gives probability setting for each channel to pass it's note.
You can use it with multi-channel clips where you want certain notes to have certain probability of passing through. So in that case you assign those notes to channel 2 or up, so you can have 8 'groups' of different probabilities this way
8 probability knobs for 8 midi channels, a midi effect for blocking or passing through notes among 8 channels by x.iso