The story's download counter counts accesses by readers during log in periods. That means that when a reader accesses a story today, that counts as one story access on their account and the story's download counters (daily, weekly and global) are incremented. If the same reader accesses the story again during the same day, their counter is not incremented, neither are the story's counters.
However, if the same reader accesses the story again the next day, then all counters are incremented; the reader's and the story's.
Chapters have download counters too, but those work differently. Due to the large number of chapters on the site and the large number of users, it becomes somewhat impossible to track who accessed what during a log in period. So due to this lack of tracking, chapter counters are incremented all the time. So if a reader accesses a chapter and then clicks the reload button on their browser, the chapter's counter gets incremented again while the story's counter doesn't.
This difference between the way downloads are counted for stories and for chapters makes the correlation between story download counts and chapter download counts impossible.