2013 Ford Focus Fuel mileage?

Ok so I bought a 2013 Ford Focus, it has a fuel tank capacity of 12.5 gallons of gas on regular I get 454 miles on a tank on mid grade I get 490 MPG on Premium I'm getting 629 MPG on 12.5 gallons. I was blown away it took me 6 months of testing to get the 629 miles per gallon, my question is this how do I get that good of mileage when the factory says it should be 41 or 42 highway? I'm I doing something wrong? I filled with the Premium grade drove 629 miles filled up and only used 10 gallons to fill up again, is anyone else getting the same results? The hours were 9 hours 19 minutes average speed was 65 MPH?

I'm hoping you are using a trip odometer and the gallons of gas from the receipt and a calculator. I hope you are not just thinking your tank should hold 12.5 gallons.
Gas mileage is really dependent on your driving habits and condition of the vehicle. If the car is in good repair and has good properly inflated tires it will do much better. New air filter and regular oil change will help. Not having any extra weight in the car will help your gas mileage.
You driving habits are like keeping under 65 MPH and not accretion and breaking excessively. If you have a car in good repair and you drive in a gas saving manner you can get over the reported MPG.