I think nut reports wrong value from the UPS.
In the screen cap from his post ups.power.nominal=5 with a 1200VA UPS (PowerWalker VI 1200 SHL), should be 1200. Same for ups.realpower=0 with load at 10%.
In general in this plugin, maybe I'm wrong, there are some mistakes in display of values for the power. Mixes of apparent power (VA) and real/true power (W), apparent power displayed in Watt and not in VA.