Trim Tracking prevents your inputs from clipping. If the input is too hot, so the pre amp would clip, Trim Tracking detects that and automatically turns the analog input trim down while making up the reduced level digitally. The level stays the same but the clipping goes away. Trim Tracking will never change your mix- it just prevents clipping.

In the trim tracking window it writes, how much db the input gain was reduced by automatic trim tracking.

I checked this levels out after the last gig and discussed it with the band member, at whom it set in. He is a very loud singer, but only during gig, not during sound check