Telaire 8002 ?

Well i bought the Co2 controller finally and im not sure if the thing is reading correctly. i live in orange california and i was wondering what kind of readings you guys are getting with outside air cuz my meter is saying around 645. i just bought this dang thing and im not even sure if its calibrated correctly. Isn;t the air outside supposed to be around 300-350 ppm? any help will be greatly appreciated.
 
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