It appears that there is a 1 to 1 correlation between tab height and fuel level (below the line). That is, to get a 6mm fuel level (below the line), you set the tab height to approximately 6mm.
When you all are doing fuel level adjustments, please record your tab-heights and post them up. It'd be good to know if this is accurate across the board.
I've used one of Drapheus' photos here to illustrate what I mean by tab height:
