Why Ohms per volt is just the reciprocal of the current needed for full-scale deflection of the meter movement, so a 50 microamp movement gives 1/0.00005 = 20,000 ohms per volt. Multiply that figure by the full-scale voltage of the range you selected and you get the total resistance the voltmeter presents to the circuit. For example, a 20,000 ohms/volt meter on the 10 V range looks like 200,000 ohms. The higher the ohms per volt, the less the meter loads the circuit and the less it disturbs the reading.
Watch out The choices about power drawn or shunt sizing confuse this with current-meter design; shunts set the range of an ammeter, while ohms per volt describes the loading resistance of a voltmeter.
Ohms per volt times volts full scale equals ohms of input resistance. Bigger ohms/volt means less circuit loading.