80 questions are divided into two sections. Usually it's not 40-40, rather 41-39 or 42-38. The 8-hour timer will start once you go to the first question. Once you finish the first 41 questions, you will have the option to take a scheduled 50-minute break. Once you submit the first section, you can't go back to the questions. The timer will stop during this break. You don't have to take the break if you don't want to, or you don't need to use all 50 minutes. After this break, the second section will start and the timer will resume. You can take a break anytime you want during your exam, but the timer won't stop.