It refers to the least significant digit on the meter on that range. As an example, lets work the math for measuring 120 volts ac on this 6000 count meter (the A to D converter goes from 0 to 5999 counts). To measure 120 volts ac, the meter will have to be on the 600.0 ac voltage range. The resolution (least significant digit) then is 0.1 volt. (120 V X 1% = 1.2 V + 3 digits) = (1.2 V + 0.3 v) = 1.5 V