The 10% date means the date which is 10% of the way through the course duration as defined by the number of days from the official class start date to the class end date. For double semester (or full year) courses where the course consists of two components – Semester A and Semester B, the 10% date is defined as being 20% of the way through the first semester component of the double semester course.  For a course that lasts for one semester, 10% is usually 2 weeks. For a full-year course (i.e. a course that runs for two semesters), 10% is usually 4 weeks.