Automatic update of max HR in Connect

You can have updates on the max HR even in activities where your maximum heart rate was not even close to the max. 

Max HR in Connect reports or activity stats = simply, registered max value.

"Max HR" in watch user profile = value calculated by algorithm (if set to auto) and used to establish HR zones. Can't view this on Connect web - only in device settings (directly or through Connect mobile).

https://support.garmin.com/en-US/?faq=FMKY5NYJJ71DbuPmFP4O7A

Thanks for the help! Now it's clear.

BTW, if I look at the daily timeline I see a max HR as 162:

while if I see the activity graph:

the max HR recorded is 167.

Why such difference? 

Furtheromre, what 6,0 z or 3,8 z states for? 

Thanks!

The daily timeline is not very accurate. It is showing more average values, and not all the peaks that are recorded in activities.

Look at "time at zones" tab....

3.8 avg = high "zone 3"

6.0 max = over "zone 5" (equal or more than calculated max HR)