...
On the Bar and Area Charts, the average time of the tasks, that have been staying in status for a given period is displayed. For example, 3 tasks out of 4 on the 24th of May were in the To-Do status for 5, 7, and 6 hours. So the average time in To-Do status for the 24th of May - (5 + 7 + 6) / 3 = 6.
...