That's not the right way to look at it (though it's very real, and it does indicate some issues you may want to address if you care about efficiency). There's a baseline static consumption, so if you have low daily consumption it's going to look worse.
There's also charging inefficiency of about 25-30% loss when charging off of 120V (I'm assuming 12A). So that 31kWh only provides ~23kWh to the vehicle battery (so, something like 110 rated miles were added in your case, using the very approximate 206Wh/mi
displayed rated miles "constant" (not the charging constant!) calculated previously from the 54.7kWh degradation threshold, but it may be a little lower in your case since your capacity may currently exceed the degradation threshold, and also the charging inefficiency estimate here will provide most of the error in this estimate).
So anyway that means you lost about 3kWh "unmetered" when parked for about 5 days. Or about 0.6kWh per day.
So if you'd driven 85 miles in one day instead, you'd have used 20kWh and wasted 0.6kWh, which is just 3% overhead (and the remaining 8kWh is charging overhead).
If you want better charging efficiency you should go to 240V/32A which will get you close to 88% efficient. So replenishing that 23kWh would have only taken 26kWh from the wall rather than 31kWh. (By the way even going to 240V/12A is a huge improvement in efficiency, so don't feel like going all the way to 32A is required to get close to the 88% efficient result. There are diminishing returns, but the curve of improvement is very steep when you're starting at 1.44kW charging.) Here's a decent rough
model (though the best-case efficiency numbers are about 4.5% high - I think the energy added was overestimated for this model due to the buffer discrepancy). The actual efficiency is published by Tesla in their EPA documents and is very clearly best-case 88-89%.
All the efficiency ratings from the EPA are with the 240V/32A maximum rate charging for the vehicle.