if you mean the dif. between an audiocontroll 190 and the tl. it depends on the ac meter. the one used in fl on the majority of the shows(it was used at sbn and inac) is from 1 to 1.5 db higher than the tl.
The one located here at Audio Visionz in Mt. Vernon is so off, I hit a 159.6 on the AC190, and SIMULTANEOUSLY hit a 143.4 on my term lab. I was playing a 51hz tone with 2 RF Power DVC 10's on a RF BD1000a1. THAT is pretty far off.