How do you reset the number of miles left on a tank of gas?

I have a 2010 mustang and I recently installed some halo headlights. I was "messing around" in the fuse box trying to find the headlight fuse after the dims went out, and my whole car reset... The radio stations went back to factory settings, the # of miles I had left (205 or so) until I ran out of gas reset. It's very annoying when it is 60 miles off of what the miles left really is... Does anyone know how to get it back to the correct amount?