that range is a basic binary octet. (256 #'s of adjustment) 0 means no light is being returned. 255 means 100% light is being returned.
there are 3 modes you need to recongnize when adjusting it. Open bolt, closed bolt and with paint. as long as there is a significant difference between them you will be fine. You can adjust it for more sensitivity when using darker shelled paint.
Some moch settings that would be more than acceptable.
Open 23
closed 55
paint 128
Lastly, jump on the web and download a manual.
http://www.armyoforr.com/downloads.html