@john.mg It looks like there might be an issue with your installation. You are required to have at least 6 inches of straight 1" pipe between the upstream shark-bite coupler and the flow meter. The shark-bite coupler is likely causing turbulence in the flow of water, which is why you’re seeing sporadic readings.
I can’t quite tell what material your supply line is made of, but it looks like a 3/4" line. Feel free to check out our 3/4" installation guide for guidance on how to fix your installation 