The table is displaying the day of the month your caches were found by various cache hunters over the years since the cache was published. It is basically just an aggregate number of finds on that day. The number can include many different cache hunters finding and logging any of your caches.
For example: I have 15 finds on 12 October. That number can represent many different cache hunters who have found any of my different caches where an online log was posted on that particular day.