There could be times when there is gap between AWR AAS and ASH AAS.
One of the most common causes is the accumulation delay of DB Time.
For a long running operations, it contributes to the DB Time when it completes.
This is called accumulation delay, which makes AWR AAS more senstive to end time of performance issue.
On the contrary, Session Count of ASH jumps up whenever sessions get stuck, which makes ASH AAS more sensitive to
the begin time of performance issue.
The gap between AWR AAS and ASH AAS could also be caused by other variables such as the AWR snapshot interval time,
ASH sampling interval time, etc.