My program start date is August 20 and I have scheduled my interview on August 24 as I am not finding earlier date. According to university some days delay is acceptable but what about my visa interview? How can I convince VO ?
You can convince the Visa officer. Carry the letter or email from University that tells that it is fine to arrive after one week. Also, if you have enrolled in courses, carry that list as well. You can try to convince that you dont want to waste 6 months and could not get visa slots. Keep trying, you can get an earlier slot, or email them for exception to give you earlier appointment.