The unused portion of tuition, fees, and other charges for veterans or eligible persons who fail to enter a course or who withdraw or discontinue prior to completion will be refunded for all amounts paid that 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.