That spring adjustment is the preload. You can fine tune that as Tunepipe said, depending on the terrain you drive on. If you do a lot of jumping, you may want to add a bit of preload. Just watch how the truck lands and see if it is bottoming out the shocks. If so, give it some more. Drive, adjust, drive, adjust. You will figure it out. It's all a personal preference, so setting yours the way someone else does may not suit your driving style/conditions.