The following labels denote the course registration status:

AN (for angemeldet): applied for registration. The participant has applied to be registered for a course.
AB (for abgelehnt): rejected. The application for registration has not been approved.
CA (for cancelled): cancelled. The course has been cancelled.
NE (for nicht erfolgreich): unsuccessful. The participant has not been successful in passing the course.
SP (for Stundenplan): timetable. The participant has added this course to their timetable.  (From the teacher's point of view: This is not an application for registration).
ST (for storniert): rejected by course leader. The application for registration has been rejected by the course leader.
SA (for Selbstablehnung): withdrawn. The participant themself has withdrawn their application for registration.
TE (for teilgenommen): attended. The participant has successfully attended the course.
V (for vorgemerkt): added to timetable. The participant has added the course to their personal timetable (participant's view), which does not entail an application for registration.
ZU (for zugelassen): admitted. The participant has been admitted to the course.

Courses with several groups (priority 1 = highest priority):

NP: rejected because of low priority. The participant has been admitted to a group he gave higher priority to.
HP: rejected because of a lack of places. The participant, however, has been admitted to a lower-priority group.

Courses within a module (selecting n from m):

MP: rejected because of the module priority set. The participant has been admitted to a course within the same module that he gave higher priority to.