From Carleton Moodle Docs
When the appointment has been attended, a grade can be given to the student's performance. This is achieved clicking on the student name in the slot list. A screen with a two tab choice will appear. The first tab (left tab) drives to the "grading summary" screen for the student:
All appointments instances for that student are shown in the form, showing comments and allowing giving a grade for that appointement.
The grade can be distributed to all the students appointed in the slot, replacing any older grade individually set for some of the students.