10 000 is maximal value and sensor displays this value if you breathe directly to it. But that doesn’t seem like an issue here.
How did you calibrated the CO2? Did you followed some guide? Can you send me a link so I could check that? I’m not sure if we ever writen this calibration publicly. It is not secret, but very few people needed calibration so it was sent mostly by emails.
Are you using
To calibrate you long press the button and then LED starts blinking. Keep the unit outside on the fresh air for around 40 minutes. The LEd then stops blinking. Ideally do not use the enclosure during calibration so air could better move inside the sensor.
During calibration the firmware sends over radio
calibration messages, can you copy all that messages from the start calibration to the end? The best is copy all MQTT messages. The Messages tab has some limit so please make sure that all messages are there, or use Node-RED debug tab where you can also see MQTT messages, there should not be a limit of number of messages.