For the sake of explanation, an example is as follows:
Assuming you score 16 points every day and deduct 15 points for the day, then on the 4th, your score for today is 1 point. However, if you do not score on the 4th, then today's score will be -15 points. In the next 15-day scoring cycle, the impact of the -15 points will continue to exist in the total score. This impact will last until the 19th, and the new 15-day cycle will eliminate the -15 point impact from the 4th.