How is the negative spring pressure set?

During inflation through the air valve on the left leg of the fork, an additional step is required for properly setting sag with appropriate negative air pressure. Charging the air valve only adds air to the positive chamber of the air spring. To inflate the negative air chamber, charge the air valve of the positive chamber at the top of the fork, a button on the bottom of the left leg opens a valve and transfers air from the positive air chamber to the negative air chamber.