Don't feel bad! It's a logical inversion/extension of the original idea (as it was explained by an above poster, at any rate) but few people seem to think that way.

If you want an idea carried off and abused to the full extent possible, I'm you're sounding board. (Although, I'm told that it makes bouncing novel ideas off of me intimidating because I WILL ask about that one thing you don't want readers to notice.)