HOw OPT works is u get total of 14 months. So, work permit limit = 12 month and 2 month= grace period. You can use the 2month grace period either as soon as u graduate (where u delay ur OPT date , 2 months after graduation) or Towards the terminal ( 2 month grace perios after OPT expiration date). I went through the same situation. I graduated in May and my opt started from July so, i didnt have any grace period left after my OPT expired. Decided to join summer classes as the best option. PS: THis information is based on what Internation Student Advisor told me abt my case.