The meter has three "legs". The belt is supposed to go above the outer ones and below the inner one. The belt tension will then flex the dial indicator and show the tension. I'd recommend printing it with a light filament color, then you can tighten one belt and use a sharpie to mark the dimple of the tension you aim for on both sides of the dial. Then tighten all your belts to see the marking through the hole in the pointer and you should be good.