[Electrickery]

That seems a bit off too much to me. I only charge on the granny but I estimate a full charge takes around 44kwh on a 38kwh battery so around 15% (estimated in that when I've checked with a watt meter a charge from say 25%-100% I've seen that a 75% charge ie28.5kwh has used 33 kwh.
Are you including the very first charge? I assume your car didn't arrive fully charged, so you had to charge it? And there is currently miles in the battery that haven't been driven yet - unless your battery is currently at 0%

 

[Electrickery]

As above, I suspect that the consumption ignores heating and cooling usage, and roundtrip from mains to battery and back to the motor losses are 10-15% so it's believable.

Certainly in the Ioniq, it includes heating/cooling as you can see the miles/kWh figure going down when you are sitting stationery with the heating on. And driving with the heating on will just give a lower figure. It should be a fairly simple calculation of just total kwh used since last reset, divided by miles driven since last reset

Losses from battery to motor should all be part of the miles/kwh figure though.