This is a bug in github classroom.
When students visit the invitation of a team project, they asked to create a new team or join an existing team.
Then, the following prompt appears.
The prompt says it is about to create a repository named <project-name>-<username>.
However, after clicking on the accept button, a repository named <project-name>-<team-name> is created.
This discrepancy should be resolved, as it is confusing for the student.