Bilinear Mesh Leveling....FADE

After I enabled a 25 point bi-linear mesh I discovered FADE. Attached is a picture of where it can be found in Configuration.h. It allows for a distance from the bed which the auto level fades to no longer compensating for the bed irregularities. 10 mm is what I have read is a good number.

UBL is below bi-linear mesh, but I have not yet figured out how to set the grid on it.