Problem with fuel gauge
 

I have a 2013 Mazda 6i. When I fill it up, the fuel gauge doesn't go all the way to full. I have to add a little more gas like I'm topping it off just to get it up there. And then when I drive, after about ten minutes the gauge will go down to near three-fourths. I'm getting normal gas mileage, so I'm just wondering if it's the gauge itself or something else.

Could be either a faulty float/sensor in the tank or the gauge itself.