Give this some time to go through the weather cycles paticularly wind in varing degrees, calm to 20 mph with occupancy. Your location in the home, the meter location, and air mixing on the home are the issues.
Usually, ventilation when +650 PPM CO2 is adequate to assure fresh air when occupied and low infiltration.
keep us posted
On a mild Saturday afternoon and with little wind and everyone home I had 1280PPM. It stayed above 1200 well into the evening.