Inaccurate gas consumption reading
 

I have a 2015 F150 Eco Boost Lariet package. The problem I'm having is when you go to the screen where it show's your trip mileage and gallon of gas used the gallon used is off by approx 3 gallons,example it might say 14 gal used but when filling up will only hold 11 gal. This also throws off the estimated gas mileage.
My question is how do you recalibrate this readings or is it something that a service tech will have to look at?