Its Salary x Game Shape(max 16). It tells you how close to maximum talent your player is this week and its why salary doesnt matter during games. Two 400k(or pick a number) DMI players are going to play at a very comparable level while ones salary could be $30000 and the other is $95000
Overall your team will play at or below the DMI average of the guys on the floor depending on stamina. One guy 3x better than all his teammates isn't going to preform even 2x better.
I usually try to get my top 5 DMI players in the starting lineup. If that means starting 3 guards or 3 PF I'll adjust tactics to fit. Usually it means Which PG do I start this week or which C comes off the bench.