Gain Structure and the level at your main Stereo Output Channel

When mixing, remember that the level at your main outs is an accumulation of the all the processing that is taking place within your mix – this ‘gain structure’ includes the level of every channel and is, of course, affected not only by the channel faders but also by the plug-ins and processing on every channel. Bearing this in mind, you should mix with the main stereo fader at its default, 0dB position and aim to keep the peaks on that main channel roughly between -12 and -4dB.

I asked a friend who is a professional mastering engineer some questions about levels of bounces from Logic and you can see his responses in the document below.