One reason can be due to our time decay function. The scores reduce over time, based on what value you set on the last X days. If you set it to 10 days, then it will decay over 10 days. The first day it will have 100 points and on the 10th day and later it will have 0 points. In between it drops by 1/10 every day. So day 2 it is 90, day 3 it is 80 etc.