Monitor height

Well it arrived, the Magnus Pro XL. Got it setup and then went about mounting my three monitor arms and my three 32” (6KG) monitors on the Secret Lab single monitor arms. That’s when I hit this problem, the first mount is in the middle, the other two are on the far left and far right respectively, but he high for the left and right seems to be 1-2” lower than my middle monitor. What am I doing wrong? Also is there a way to get the middle monitor to sit further back? My guess is I have to offset the arm but if someone could confirm? Thanks