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The easiest way i find (if possible) to set up my mixer is to max out the channel faders and use the gains to set them so the track peaks at around 0dB.
I then set my sound card input volume so that soundforge peaks at around -5dB when my mixer peaks at 0dB. This gives enough room for any transient increases in output whilst mixing and any inaccuracy in my channel metering.
The way a mixer should logically work is that if you have the channel and master faders at maximum, and you meter the channel to 0dB then the whole signal should be outputted at 0dB (assuming this is the nominal level of your main/rec out).