Not quite sure I understand that (how does it record distance by seconds?) but will check out the settings in the instruction manual again.
Have had various results in accuracy. Did a 16 miler yesterday, ran 8 miles, turned around and came back, finished in same spot but only recorded 15.91 miles. However, at the Dartford 10 clocked 10.01 miles.
And likewise for the Wokingham Half, i'll be taking part but there would have to be a serious amount of people taking a wrong turn for me to get near the podium!