I reset all previous calibration and started off fresh with Nike+ GPS app again this morning, here it showed 5.26k
while Garmin 410 showed 5.06k exactly as before. In fact the turning back point at 2.5k was in fact a bit earlier than my last run. Garmin also showed a slight difference in elevation gain of 12m between 2 runs.
I guess an error of 3.95% isn’t too bad (assuming Garmin is right).
I’ll do a longer run this Sunday with Garmin and Nike+ GPS app.