Hello,
Your explanation is somehow correct, but I think the real PMP exam starts at 230. When the question 60 is answered (it is supposed to take 75 min exactly), the time is stopped at 155 min. whether you take advantage of 10 min or not, when you start the exam again the monitor show you the question 61 and the total remaining time is 155 min.
Again, when the question 120 is answered (it is supposed to take 75 min exactly), the time is stopped at 80 min, in 10 min, the exam starts in question 121 and the total remaining time is 80 min.