I took the usual "split" stops to adjust wardrobe. I pause my stop-watch and restart my run where I stopped the watch.
My first mile is typically the slowest part of my run. Today my stride smoothed-up within fifty yards of starting and I ran z 13:26 mile. The second split was 26:40.
I ran a marked 3.1 miles (5k) rather than a shorter distance and scaling the times.