Oops.
I just checked both Yahoo Maps and Mapquest, and it was only a 2-mile run. My bad.
I remember checking a couple of weeks ago, and the 2-mile number stuck in my head. Guess it was the round-trip number, but I misremembered it as the one-way mileage. Then, this morning (my first run not on a machine in weeks), I doubled what I thought was the one-way mileage.