Coventry manager Chris Coleman didn't understand it.
Wolves boss Mick McCarthy understood it even less.
Sylvan Ebanks-Blake didn't even try.
Steve Bennett may have understood it, and his assistant certainly did.
After all, it was his decision to allow Sylvan Ebanks-Blakes winner to stand after re-entering the field of play in what looked to be an offside position to nod in Michael Kightly's spilled shot.
OK, a clearly offside position.
The logic, and apparently the rule that applied goes, that as it was SEB's momentum that had taken him off the pitch, and not a desire to gain an advantage when he stepped back on the pitch he wasn't offside, despite the fact that he was.
It's easy to see where the confusion lies.
Odd that Coleman wasn't quite so confused over why Chris Iwelumo's perfectly good strike was later ruled out by Mr Bennett.
Or why a first half penalty for hand ball was denied as well.
But in the world of football, managers are well versed in applying selective myopia to incidents that go in their favour, whilst becoming eagle eyed when the fortunes are reversed.
Which is why it was refreshing to hear Mick McCarthy side with the unfortunate Coleman in questioning the magic rule that gifted Ebanks-Blake Wolves decisive goal.
Whatever the reason, whatever the rule, SEB's header stood, and Wolves took a very hard fought three points off a Coventry side that gave us a run for our money all day.
But you don't win any prizes for being a strong runner, what usually matters is the position you're in when you cross the line.
Or not, as the case may be.