Whoa. This is even more weird than I thought.
It is a first generation UMC, as I can see from the adapter plug shape; mine is too. But they are all supposed to signal the proper number of amps. The way they work is that they have a small resistor inside the adapter with various values. The main box in the UMC detects for what that resistor value is, and knows the proper current limit to announce to the car.
Now the really weird thing from your pictures is that when the UMC sends the amp signal, it announces that as a maximum. So yours should be showing "12 / 12" if that adapter were working properly. That would be using the full 12 amps out of 12 maximum allowable. Yours is showing 15 / 32. That 32A upper limit is very strange. On the 1st gen UMC in the USA, they never made any that would use a 32A limit. The higher power ones like 6-50 and 14-50 would announce a 40A limit. Canada had some trouble with the national electrical authority, and they had to replace everyone's 50 amp adapter types with ones that internally had a different resistor that would signal for a 32A limit. But you are in Texas, not Canada, and that's not a 50A plug type anyway, so irrelevant. That is definitely defective somehow.
As for what you are doing and should do, it depends on what that outlet really is. You are only supposed to run 80% continuously of what the actual circuit rating is. So for a 15A circuit, you can use 12. For a 20A circuit, you can use 16. A lot of circuits in modern houses are run as 20A circuits, and code allows a mix of 15 or 20 amp physical outlet types on them. So even though that outlet may look like a 5-15, it might be on a 20A circuit, and your 15A level could be OK.
But if that outlet really is on a 15A circuit, that is probably thinner wire, and using it at the full 100% capacity of 15A continuously is dangerous, and you need to turn that down to 12.
