I have a similar gripe with my P3D+. Not quite as bad as this but even starting off at 100% and pulling in at “1%” my max used hasn’t even touched 70kWh.
OTOH, It will go all the way up to “299mi” at full charge.
I think you have a 2020 P3D+.
Was that 100% to 1% in one continuous drive? If not, you could lose significant energy when the car sits.
You would expect to see (assuming you have 77.6kWh = 260Wh/rmi*299rmi; you may have more):
77.6kWh*0.955 = 74.1kWh (buffer is 4.5%, below 0%)
You use 0.99 of that:
The trip meter always shows a 1-2% loss:
0.98*73.4kWh = 71.9kWh
So the max I would expect you would see on the trip meter would be about 72-73kWh, for a brand new car. You saw less than 70kWh, which implies to me that the car must have spent some time sitting and losing energy. Could also be some error on the % used - rated miles would give better accuracy.
However, this method of tracking capacity is completely different from what the OP was observing. It is definitely well worth doing and capturing the data though - it is one of the only ways to capture degradation over time - you can always go back to your pictures and see how much energy you were able to pull out of your new battery, and compare.