An unexpected reset

Odometer: 2844.4
Tank Mileage: 608.9
Gallons Added: 15.578
Long-Term Average: 40.5 (reset during tank)
Short-Term Average: 40.5 (reset during tank)
Calculated Average: 39.1

I will need to figure out how I'm going to calculate, and report, long-term average mileage. One of the sites I'm recording my mileage on reports my overall average as 37.7 mpg.

Between the time we parked to go to lunch and the time I started the car after lunch, several items were reset: short-term average, long-term average, the dash display settings, and the fuel efficiency display settings. Trip A and Trip B were not reset. I have no idea what triggered this reset and no operational impact has been noted, but it is annoying.

I had 10 miles to E showing when I stopped. I already knew the low-fuel warning activated at 50 miles to E. This is accompanied by an alert tone. This tone is repeated at 25 and 10 miles to E. One thing that will make me feel better is that I drove more than 40 miles after the 50-mile warning. Fuel remaining goes down quickly from 1/4 to the low-fuel warning, but the slope appears better after that point.