Not sure if this has been mentioned somewhere else already, but there appears to be an error in the text for the upgrade instructions email. It is a minor error, but could be confusing to some people.
It currently reads
Upgrade by visiting \admin\docker, refreshing the page a few times, and pressing the "upgrade" button.
and probably should read
Upgrade by visiting /admin/docker, refreshing the page a few times, and pressing the "upgrade" button.
I would submit a pull request myself, but I could not find where the text was located.