What counts as a mile on a standard 400yrd track? 4 laps on the inside lane, or 4 laps on the outside lane...?

There aren't any standard 400 yard tracks, not in track anyway, tracks are 400 meters. But assuming you have a 400 yard track (which is measured from the inside of the inside lane), a mile is 1760 yards so it would be 4 laps and 160 more yards or 40% of the track.