It doesn’t report usable kWh, but it does report charging speed in kW while charging.Expect a few % - maybe as much as 15%? loss between what comes out of your domestic grid meter, and what's available from you rHV battery to drive with.
E.g. Ampera takes 12 kWh from the grid, to give me 10.4 kWh I can drive with.
All down to inefficiencies accumulating along the way; heat lost in wiring from Consumer Unit, rectifying & transforming mains AC to around 400+ Volts DC, heating in the wiring in car, heating thx to resistance inside the battery, chemical inefficiencies (I guess heats the battery?).
If the car's reporting what you'll be able to take out of the battery when driving (nice if so!), there's also the inefficience to add-in, when the chemistry pumps those electrons, so again there's more heat lost inside battery. It all adds up!