I'm trying to find out, what is the coolant temperature when the needle hits the 1/2 way mark?

Took my car to a radiator shop and they put in a thermostat that is set to open at 192-195 when the factory spec calls for 172. I have been having issues with the needle moving around and even slightly above 1/2 and want to see if it is all b/c they messed with the thermostat. It never varied before they did this and held steady below the 1/2. If I'm sitting at a light and rev the engine, it drops down quite fast (air not bled out of system?).
on a sidenote, I did a compression test and it was an even 180-185 across all 4 cylinders so it doesn't appear to be a head gasket issue.