S8 CO2 reading low like 89

I removed SHT30, PM2 sensors, OLED displays.
Using serial port I am reading the S8 CO2 values.
It is very low like 89. I ran this every day for like 15 minutes as I am working on wi-fi set up as the next step.
Could someone share some info on this?

After running it for a few hours, it is now reading around 580.