Mr Bojangles
Midfield
That's what the marker is for. It helps determine the distance the putt goes. EG, you have a 10ft putt going 2" uphill, move the marker to 15ft.Don't use the marker at all, just the grids. I'm just on about how ridiculous the rolls are sometimes after a tiny tap.
The maths are putt distance, plus 1.5 x uphill distance, plus another 2 feet. Downhill is slightly different but have a play about with it.