Meijer

I arrived on 1-23-19 at the Meijer fuel station #154 on 8225 E. 96th Street, Indpls, IN 317-585-2429 at 1:19 pm. Price of Diesel on this day was 2.599 per gallon. I went to the Diesel pump to fuel up. I was on pump #12. My truck says I should be getting 19.3 gallons of fuel. I figure that that number might be a little off by a half gallon or so. So I filled up and then looked at the pump. The pump says that I was charged for 25.932 gallons a 6.632 gallons over what I should have received. That is a $17.23 dollar over charge. Can you explain this for me please so I better understand why we, the consumer, are being way over charged? And how do I receive the over charge back?