Of course it varies for "civilian" devices from EBay.
They put that count into NRC report. It means that it has pretty specific calibrated meaning for that regulated environment.
>However, even if we accept 100 as the background CPM value, 300 on 100 does not represent significant contamination in a typical environment (but does imply some occurred).
report mentions 300 clearly as something above normal, whatever normal is there. And that is after decontamination. Clearly the source of contamination - the pool - is much higher than 300.
