From the Holley guide at:
http://holley.com/data/Products/Technical/199R10321.pdf
1. If you do need to adjust this, loosen the lock screw and turn the adjusting nut clockwise to lower the fuel level and
counter-clockwise to raise the fuel level.
2. Tighten the lock screw while holding the adjustment nut. Make sure the fuel level is mid-level to slightly below center of the
sight glass.