[DCP-o-matic] channel sound gain

Looks like when I change the gain for a sigle channel is not showing up in the Show Audio graphic. Also, the channel gain overrides the general gain or is relative to the other channels? Let's say I have a general gain of -10dB and center channel is -5dB, will center channel be -10dB or -15dB? Just to make it harder, it's an stereo source upmixed to 5.1 (up-mixer A) v. 2.0.41 Thanks! Manuel AC