Running premium pump gas it should be set at 0. (engine must be running to adjust) It does the same thing as a timing key, it advances or retards when during compression the spark fires. Advanced timing requires higher octane fuel.
The Z 440 SnoPro racers are equipped with the same shocks as the ZR 440 Sno Pro racers. I would take a pic of the rear crosslink shock but my setup is updated the the better version off an '04 440 SnoPro. (larger shock diameters and 1 reservoir instead of 2)
The first 2 pics show the stock '02 setup. The third pic is the updated version that I have.