If the OP is still following this thread:
The simplest fix would be to buy a compatible Grip Shift setup (i.e., one with the same cable pull ratio) from a lower model tier, one that shows the gear numbers. I've put many thousands of miles on a 1995 Cannondale hybrid with lower-level numbered Grip Shift shifters, and they still work perfectly, so the quality is there.
If you buy just the right-side shifter, which I imagine is the one you really need, it should cost around $30 or under. Very easy to install and adjust. Watch a couple of YouTube videos if in doubt.