Clip louder than it should be if pan mode set to "none" vs Stereo Left/Right

Hi all,

I'm curious if someone can shed some light on this. I pulled in a pink noise sample (this is a sound sample that is constant noise at -20db used to calibrate speakers). I then pulled up the Multimeter in FCPX (via the Audio effects, Speciliazed option). I played the sound sample clip and the RMS level on the meter (the one that handles averages...versus peaks seen in the normal meter) showed it pegged at a constant -15 db. After scratching head for awhile, I tried a few things, and switching the pan mode of the clip from "None" to "Stereo Left/Right" caused the clip to come in at the -20db it should have originally.

Does anyone know why the clip will play too loud if Pan Mode is set to "None"? I guess I need to set all my clips to Pan Mode "Stereo Left/Right" at the beginning of an edit? Am I missing something here?

Thanks,
Matt