Inaccurate Data on the app

9297537 said:

the map shows 21km but the app records, 20.38?

Can you post a link to the activity from Garmin Connect Web?  And/or zip then attach the corresponding fit file from the \GARMIN\ACTIVITY folder from your device.

connect.garmin.com/.../6534179695

You'll need to change the privacy settings to "Everyone," at least temporarily.

I have.

Thanks for the attempt to assist. 

Everyone I ran with recorded 21, Suunto guys as well, it was only when I checked my app, which automatically syncs if I'm closer to the phone where i then saw 20:38. I updated the app settings but it was still strange. I'll attempt another activity in the morning and see whether this would still be the case.

Why don't you make the Activity visible to Everyone as seilogramp asked, so that we can have a look, and try to help? Just click the link you provided, and then select Everyone under the Padlock icon, exactly as on the screenshot.

... anyway, if you are sure about the distance, you can simply open the activity, and edit the total distance to match the reality.

Thanks. 

It's no trainmash, it had been a training run. It had seemed strange hence my enquiry on the platform. I did open up my privacy settings a while back. I'll just observe whether it persist or not.

9297537 said:

The watch beeped 21km, the map shows 21km but the app records, 20.38?

Probably more correct is the watch beeped for 21 laps and the map shows 21 laps. With an assumption that all completed laps are 1,000m (1km), the total recorded distance would be assumed to be 21.02km and not 20.38km.

The problem is at lap 16, which is only 360m, giving you the recorded distance of 20.38km.

Lap 16 may be short because you accidentally pressed the lap key, but that still does not explain the overall shortfall of ~640m.