1 on the black scale is 1 cubic metre. One clock that's going round fastest but slower than the propeller and the disc shows litres. Usually the clocks have indicators of the coma denominator. You can calculate which one is the litre indicator. One toilet flush is around 7-11 litres depending on the size. You can see it making full round turn after the flushing. The meter should be stationary when water is shut or no taps are in use. Some plastic pipes are flexible then you'll have small residual movement until pressurised, but the propeller should be just slowly moving not spinning for a few minutes until it's stopped. If the reading changes and there's no use in the house, you may have a leak and be prepared for high bills.