I guess you mean you have 10mm of tube sticking up through the top yoke? At the need of the day, its your decision, but riders do things to bikes to try to improve them, as they see it. It may be that the rear suspension has been lowered, or a different shock fitted, and the front has been lowered in conjunction with that. Or perhaps a previous owner had short legs and lowered them to get more foot on the deck. Lowering the front has the effect of making the bike turn in a little quicker. Its an easy piece of work to set it back up to stock, or try lowering it a little more and see if you can feel the difference. Trial and error to suit you and your riding "style" really. Mines lowered 35mm at the rear and 30mm at the front