Limiter question

I have a finished stereo mix and I'm sending it to the Master bus which has a limiter in it. I'm trying to get a finished mix volume. 
 
The limiter can show a level of -7 when the Master bus is already in the red. That's what I don't understand, one set of meters can't be right.
 
I've tried a two or three limiters and it's the same each time, the Master is in the red sometimes before the limiter is showing any compression at all. What's the explanation?
 
Thanks - rev

John:
 
Thanks. In this case it's the only plug in the chain, but I see no way to set Pre or Post. How do you do that?

+1