You can forward and backward run the clock. When counting up, it goes only to 99 minutes. After the minute is again 00. If you want to determine the duration of an event, which lasts for example, 3.5 hours (= 210 minutes), then stands on the clock 10. But you do not know if it's 10, 110 or 210. Since the numbers are very large, it would certainly have been possible, the minutes 3 digits counting. However, for most events are likely to 99 minutes are sufficient. Therefore, the full number of points.
