In the “Add New Members” screen, it states, “You can add 20 more people.” which a lot of users mistake as you can only add 20 more people to the channel total. Suggest changing the wording to make it more clear to something like, “You can add 20 more people (at once).” Just an example, I’m sure there’s a better way to word it. 
Thank you for the feedback, would you like to share this idea on our feature request forum here https://mattermost.uservoice.com/forums/306457-general?