Once you have marked yourself as having discontinued, your teacher will see the information in Sisu. This will help the teacher, as teachers need up-to-date information on who is taking a course. Instructions on dropping a course are available from the Student Guide. 

No mark will go into your transcript of records to show that you have discontinued a course. Discontinuing a course will also not prevent you from registering for the same course again, if you want to take it at a later time.