Marketing Channels Sum of Visits more than Total Visits

It is my understanding that Marketing Channels is a waterfall, and each Visit will fall into ONLY one Marketing Channel, from the Marketing Channel rules.

All Mktg Channels have the override checked - EXCEPT for Direct and Session Refresh (Internal Referrers).

Is there something that needs to be changed here so that the Processing Rules only allow 1 Last Touch Marketing Channel per visit?