Hey thanks for going into detail - I'm definitely interested in how it all works. That is eye-openiing for sure.
I think I'm more concerned about someone making $2.12 an hour and relying on tips to stay afloat, along with how you've described they can be punished by having busy shifts taken away from then, but the social aspect of it was definitely why I asked my brother. 15% sounds like a good rule, bump it up when applicable.
As usual, Hubski rams home how good I have it in my little corner of the world.