2x3 miles CAN This be correct?

I ran this workout outdoors, and it was too dark to see my splits until I got home (so i ran by feel). I was surprised at the results enough to doubt the GPS...



Set 1 AVG heart rate 81% of MAX
5:10
5:27
4:41

(I find this last mile REALLY hard to believe. However, since I ran an extra 1/2 mile to make sure I did not cut the repeat too short, I know it was a full mile split, unless the GPS crapped out and gave me a short half)

Set 2 AVG HR 83% of MAX
5:23
5:29
5:44


Thats 2 5k PR's back to back.