It's all about when different fields are incremented
CallAnswered is incremented once a call is answered
The total you are mentioning seems to be under the "Completed Tasks", which means it is incremented once a call is finished totally
So, if we take a call that was answered at 8:25 and its duration was for 10 minutes (lasted till 8:35)
It will be "Answered" in the 8 oclock interval, and handled in the 8:30 interval
eventually, at the end of the day, you should have both total values equal
i hope this helps