Audio control surface

I purchased a behringer xtouch control surface to use with resolve, which was recommended by Peter Chamberlin on another forum. It has motorized faders and for the most part works well in resolve. My only issue is the main/master fader on the behringer doesn’t control the main/master fader in resolve. If I have 2 audio channels in resolve for example, the control surface will use the 3rd fader to control the main. Or if I had 6 channels in resolve, the 7th fader on the Behringer would control the main and so on. Peter and team, is this a bug or is this the way it should work? Seems a bit odd.