It's a relative measure that gives you a quick and dirty look answering the question about whether a player does something on the court when they get time.
In this thread, Woody's per 40 numbers are pretty impressive. In contrast, JBA's per 40 numbers suck out loud.
The per 40 numbers help make an easy comparison verifying what the eyes see - when Woody played, things happened. In fact, a pretty good trend of things happened. When JBA plays, his stat accumulation is minutes.
It's the same with Jesse. I was bullish on his improvement because even though he played sparingly as a freshman, things happened.
I'm not arguing anything related to walk-ons and nobody actually cares about per 40s of dudes not on scholarship.
OrangeDW made a good case that when Woody played here, he played well, and the per 40 numbers support that. It's weird people are arguing that or just not getting it.