Thanks for the explanation above. Not trying to be a whiner, just frustrated by how un-intuitive things seem to me now, especially the shifts page.
I'm a programmer, not an interaction designer. But I'm trying.

The feedback is a great help.
We'll get there.
PPLNS in general (shifts actually simplify it for reporting) is hard to explain in a table. If I were a graphics designer it would take me no time at all. I think the key to explaining PPLNS relies in either a real-time conversation, a LOT of images, or the best way: an animation.
A simple GIF could probably clear up PPLNS misunderstandings in under 15 seconds :/.