The refund of the unused portion of tuition, fees, and other charges for veterans or eligible persons who fail to enter a course or withdraw or discontinue prior to completion will be made for all amounts paid which exceed the approximate pro-rata portion of the total charges that the length of the completed portion of the course bears to the total length of the course. The pro-ration will be determined on the ratio of the number of days or hours of instruction completed by the student to the total number of instructional days or hours in the course.