There are 4 readings regarding the fuel average in Aqua.
1.Upon pressing "Disp" button, there's a km/l reading with "AVG" written above it. When this is visible, press "Trip" button to switch between the following:
Average for Trip A - i reset my Trip A on refuelling so for me this reading for me reflects average since last re-fuelling.
Average for Trip B - i reset my Trip B on Oil change so for me this reading reflects average since last oil change.
- Average of current car power-on cycle.
2.Upon pressing "Disp" button, there's a km'l reading WITHOUT "AVG" written above, this is the instantaneous fuel average and shows 99.9 when the car is in EV mode.
Hope this helps.