The College Accelerator Edition includes two ACE proctored exams per 30 days. Your 2 available exams reset on your billing date. Additional exams are available to purchase. They roll over month to month, so you do not have to worry about losing any exams you purchase.
Passing two exams is equivalent to earning 6 transferable college credits. If for some reason you don't meet the 70% minimum score to pass an exam, you can retake it again in 3 days.