When you run more than 5km, your Garmin running watch will look for the fastest stretch of 5km within that tracked activity, and use it as the basis for determining if you have a personal record.
Not all Garmin devices extract the best time for a section within a longer activity(my 310XT certainly does not!)Interesting. I didn't know that. I can only go by my experience, and I only have a Forerunner 235. So far it has not done anything defying expectations with regard to determining my ‘achievements’/personal records after runs.
Not all Garmin devices extract the best time for a section within a longer activity(my 310XT certainly does not!)
Garmin Connect takes the time for the total activity if the distance is "close" to a distance for which "personal records" are recorded - see this quote from GC:
"Personal Records are created when you upload data that closely matches one of our predetermined distances, and it's the fastest time you've ever uploaded for that distance.
You don't have to exactly match a distance, but it must be close. (For example, a Half Marathon Personal Record may be created if your activity is 13.2 miles.)"
As far as I understand, GC works exactly as you described - you have to be quite precise in distance to set activity as PR.
From my experience, it will be recorded as a new PR for 10 km :) but not for 5.
To match PR's on GC, you have to match distances closely.
At least it has always worked ike that for me. This is why I have started using Strava too - it is quite more flexible.