How to I determine/ interpret values of autoranging multimter
Look up voltage curves for the chemistry of your batteries. Depends on the exact battery, but you can gauge how much power is left based on the voltage:



From this graph, when it reads 1.0V, there is roughly 20% power left, and when it reads 0.8V, roughly 5% power left. Of course, it's hard to extract 100% of the power from a battery, since many devices require a certain voltage level to operate, and when it drops too low, they cannot run. Depends on the design of the device.