Sounds like the gage is wonky not you. Just check your water, and keep it at a certain level. I only need to add more every other to ever 3rd day. Don't panic. Just don't let it go dry for very long and too much water is not good either. The chicks can drown in their shells (been there and done that). Ive been hatching for 27 years. Long before the there was humidity reading. To be honest I had less problems before all the gadgets came out.
Good luck, I'm sure you will be fine.
Good luck, I'm sure you will be fine.