You can use this screen to directly manage the attendance codes used by teachers in your group. The attendance codes you define are the default attendance codes uses by all teachers that join your group. If you want to make sure all of your teachers use the same attendance codes, you should setup your attendance codes and make sure they are correct before teachers are allowed to join your group. The attendance codes you define do not automatically affect the codes available to teachers who are already in your group because that would invalidate the attendance they have already recorded. However, teachers who were already in your group prior to the time you defined attendance codes can go to their attendance definitions screen and click a link to have all of their attendance records deleted and their attendance codes replaced with the attendance codes that you have defined.
This screen has some extra abilities not available via file based integration. As opposed to the file based uploads, this screen lets you add new codes without forcing all teachers to resynchronize/delete their attendance and you can change values associated with a code (but not the code itself) without forcing teachers to resynchronize/delete their attendance.