On a previous car, fueled it up shortly after the fuel light warning came on. After filling, figured at the light coming on situation in reality had over 4 gallons left in tank. The car was avg 21 miles per gallon. Multiplying 4 X 21 =84 miles of travel left in the fuel tank. To be on the safe side, when first noticing the fuel light on figured there was 50 miles to empty, before hitting that mileage, pulled up to the pumps before 40 miles were traveled to refuel.

The cruising range left in the tank could purposely be made to show less miles then actually be left in the tank. Would guess to say the manufacturer uses this as a safety buffer. They don't want the vehicle user to run the tank near the cruising range prediction and run out of gas a few miles before the miles limit was reached. Manufacturers don't want complaints on cruising range prediction. We all know we have different driving habits, terrain, temps, snowy, slow down conditions that can vary our normal driving range by miles.