Your Personal Bests card auto-detects one row per standard distance (5K, 10K, half, marathon) plus any custom distances you’ve added, from your race history. The strongest signal it uses is your activity’s Workout Type set to Race on Strava — if a race isn’t showing up as a PB candidate, that’s the first thing to check.
parkrun is its own distance, separate from open 5K — matching how results work on Power of 10, a parkrun never counts as (or displaces) your open 5K PB, and vice versa. This trips people up occasionally, so worth knowing going in.
If a PB is wrong, or you’d rather a different run held it, the 
Manage page’s PB picker lets you:
- override which race counts as the PB for a distance,
- temporarily exclude a race from PB consideration,
- add custom distances (10 miles, 30K, etc.), and
- anchor a PB to a manual / no-GPS activity you logged by hand — for example an old track race you ran without a watch. The picker lists these alongside your GPS-detected races.
Saving refreshes your PB card within a few minutes.
About the green ✓ — it means a time is ratified on powerof10.uk, the UK’s official results database. Where a ratified result exists, its official chip time is what’s shown and ranked on, even if you’ve manually curated a time for that race yourself — it’s the more authoritative source. Hover the checkmark to see the chip time (and gun time too, if different). A small number of PBs show a Po10 tag instead of a checkmark — these are ratified results with no matching GPS activity at all (e.g. an old track race run without a watch), pulled in from Power of 10 alone.
Full explanation: Personal Bests and Manage Page in the guide.