Excellent! I have the same one as @Lornakins but mine tested exactly 1500 when I did the 1500 test so I didn't worry about it.
My directions only say that we should calibrate it and that it was factory tested and is accurate, but that it may need to be re-calibrated. But it does not say how.
I will look online and see if I can find anything. But yeah I agree she should test again. @Majiktoker