Imagine that you've properly connected your multimeter into an operating circuit, and the meter's function/range switch is set to read DC voltage in the 20 V range. The meter displays a "1" in the most significant digit position. This indicates that

If the meter is set to read DC voltage in the 20 volt range and it displays a 1 then it should mean 1 volt assuming that the maximum reading would be 20 volts at that setting. But if it is only around 1 volt is might be more accurate to set it at say 2V range to get say 1.6 actual volts.