Disconnect the air supply to the rotary.
Put the dial indicator on the rotary as shown in the illustration.
Use an aluminium pry bar (approx. 1" X 1/2" X 18") to push down the spindle  at about 15 ft-lb (20 N-m), and then release. Set the indicator dial to 0.
Use the pry bar to push up the spindle  at about 15 ft-lb (20 N-m), and then release.
If the indicator shows more than 0.0005" (0.01 mm), the adjustment of the spindle backlash is necessary.
For this adjustment you must send the rotary to a certified rotary repair facility.
For instructions on where to find a rotary repair facility and how to send your rotary unit, go to www.haascnc.com.