How Hand2Note distinguishes a fish and a reg you can find here:
The Regular and the fish in Hand2Note
Range Research intended to explore pool of players to get pool's weighted average values for all stats in the report. Every of these players have different amount of hands which also have intersection. So, stat "Hands" can't be useful for Range Research.
You can create any Stats in Filter Editor and add them to your Popup that is assigned for specified Game Type in Range Research:
You can see what Popup assigned for your Game Type and change it if necessary in Configurator-> GameTypes:
Do not forget to rebuild the statistics after new stats will be created and added to your Popup.