It adjusts to show the gap at the bridge location in relation to the plane of the upper bout (along the aluminum bar). Different folks use different gaps dependent on the scale and size of the guitar.
_________________
My Facebook Guitar Page"There's really no wrong way, as long as the results are what's desired." Charles Fox
"We have to constantly remind ourselves what we're doing....No Luthier is putting a man on the moon!" Harry Fleishman
"Generosity is always different in the eye of the person who didn't receive anything, but who wanted some." Waddy Thomson