Open the OpenSCAD file and tune for your printer. It assumes your bed is square, but you can always do the short side or scale it in the slicer. It is helpful to set the square count to the number of autolevel points you use. Note the edges get a trimmed down square so you don't get too close to the bed edge.

Speaking of, I usually let it go at a few mm of height and scale the Z until I get a 3 or 4 layer slice.

Once it prints, carefully look at the top (picture is good) and then peel off carefully and look at the bottom. You'll see exactly where your bed needs a little more tuning.