It's not stone related.On the bottom bar that goes up and has the number increase, what's that? Your stone power? and what does the levels mean?
You can spend one bar to do a special move.. usually something like quarter circle forward LP+HP (or LK+HK). You can do a super move that uses 3 bars , for Hulk this is quarter circle backward LP+HP.
If you're played street fighter 5 it acts similar to the EX bar.