What does the message "The specified username is already in use" mean?

Usernames are unique in the entire Coaches Console database, so if you are shown this alert message when you create a username for a contact, that means either you use this username for another contact or another coach uses that particular username for one of their own clients. What you can do to solve the problem is to alter a bit the username value, like maybe adding a number to it (e.g.: "johnsmith102" instead of the "johnsmith" that triggered the alert message).