If the signal you are getting is a train of pulses, then it is the correct signal. If it is the raw firing wire, then you might be getting a pulse every time a piston goes down, not every time the shaft rotates.
As for modifying the board, you dont have to. It will work at a lower resolution. However if you want a higher resolution over a smaller range, then you modify the components. I would get it working without modification before attempting to "improve" it.