The sum of users in a report does not add up to the total found by adding the number of users in the Google Analytics UI.
Connector: Google Analytics
It is not recommended that you add the number of users in Google Analytics. This is because a single user can have multiple sessions (i.e., a user can log in at various times). Every time they visit your site, even if it is the same user, they would be counted as a new user. For more information on this metric please visit this article.