i have a check source that have checked with other calibrated gm meters.the source has 2000 cpm and is 2 mr/h .when i test with the 300 the cpm is correct.but the microsieverts says 3.721 or around that.it should say 20.000.when i calibrate it to read 20.000 the display shows a minus - symbol in front of the 20.000 and the microseivert reading has a double hh after it.is the screen messed up?or am i calibrating it wrong?any help you can give would much appreciated.thanks