The tested flow is what that plate flowed on my bench, don't use that figure for your calibration though. I should have stated that is for reference only.
On the smaller dia plates my bench is not flowing correctly either, I'm fighting a "battle" with mine also? I haven't had time to spend looking for the problem on my bench. I think it has something to do with the airflow in my shop with the heater blowing. I only use one plate on my bench to calibrate the FP1 setup, my readings are consistant from day to day so I've only been concerned with that for the time being.