A QUICK WORD OF WARNING: DO NOT ATTEMPT TO USE THIS BALANCE TO MEASURE OUT 1mg of a something if being off by 1 or 2 mg could be dangerous, just don't do it with this device. Instead measure out 100mg then dissolve in solution.
Despite the quite excellent accuracy of this scale over its whole range it simply is NOT the tool you need to measure out a 1 mg sample.

I would suggest trying to measure at least 10mg of a sample if you are measuring by difference (i.e. you put X mg on the scale, tare it, then remove sample until you reach -10mg) and >30mg for normal measures.