Yeah.. i just seem to randomly moving those sliders up and down. however..... i have a theory. Ive noticed that when i do finally hit for example Copper ore.. if i leave the slider there and keep mining i get copper ore again or equivalent good stuff. The slider may be a sweet spot finder. There may be one good spot on the slider. and you have to move it up or down to find it. If your getting worms(mining). Try moving the slider til you get better stuff
Ya, it doesn't really seem to be all that significant. You could mess around with it trying to find the sweet spot and use up all of your attempts in the process. Generally speaking, I only move it if I pull up crap whether I'm mining or logging.