Q: apple watch gains 3 minutes after I take it off charger

That may happen if your Apple Watch OS and iPhone iOS are not up to date.

Instructions here > Update the software on your Apple Watch

Hi there!

Have you adjusted the time within the watch settings, to set it ahead by 3 minutes?

Thanks,

Alex

Hi

The following steps may help:

• Check the Time setting on each watch:
  • When viewing the time on the watch face, go to the Home screen (via a single press of the Digital Crown) > Settings (cog icon) > Time.
  • If this setting shows +3 min (or anything else besides +0 min), tap on it and adjust it back to +0 min by turning the Digital Crown, then tapping on Set. 
  • This setting affects the time shown on the watch face except when the watch is in Nightstand Mode, when the actual time is shown.

• Check that you are not using Time Travel by accidentally turning the Digital Crown as you remove the watch from the charger.
  • https://help.apple.com/watch/#/apde3ebe2997