Print3D addon questions

I have a simple model that’s basically a fancy stick and I’m running the Print3D addon against it. I can’t figure out a couple of the results.

First (see first pic below), there’s an item in the addon panel called Zero Faces and the addon flags what seems to me to be a random selection of faces. “Zero Faces” is not documented on the addon page so can someone tell me what it means?

Second (pic below), the addon flags some faces as “thin” but the model is a solid. I’d welcome an explanation for this, too.


PS. pix show just one end of my fancy stick, and don’t show all the flagged faces.