Garmin overall average pace and splits average pace don't add up

Hi - from my 5 mile run today here is my average pace for each 1 mile segment and then my overall average pace at the bottom as reported by Garmin. Splits are every 1 mile:

split 1: 10:02 min / mile
split 2: 9:55 min / mile
split 3: 10:08 min / mile
split 4: 10:13 min / mile
split 5: 10:01 min / mile
average pace: 10:00 min / mile

Now my maths is not that great but how can this be? Any ideas?

the 6th split was 1.5 seconds long - i.e. i stopped the watch 1.5 seconds after i hit 5 miles. It does show up at a mega fast pace of 5:45 min/mile but distance is zero so it should not effect ther results.

I think that they measure the position every few seconds, and record the lap the first time that the distance exceeds a mile, rather than interpolating between points. Certainly with mine it's usually got to x.01 miles beforew it gets round to beeping. That difference may be enough to explain it.

Your mileage may vary...