This option will reset the rotations for all Courses in a given year. If two Courses in the same year have been created without rotation numbers then only one of the Courses will inherit the Student Groups. If this is an issue, you can do a Group rebuild based on the Registrar's roster.
The primary reason to run this report is to reset the rotation numbers of Courses if those Courses and been added or removed from Leo in such a way that the rotation numbering logic was not used. This could be due to a custom routine to import or remove users, direct update of the database, etc.
It is important to note that when a Course's rotations are reset, they are reset for all years of that Course. Thus, this will affect years other than the selected year.
Path: Admin Toolbar > Course Management > Course Settings > Courses > Reset Rotations