As tony said if its A5, don't worry about it,
One thing you can do is open up the queue message, scroll all the way down to the bottom and double click the last message, this will be your oldest message, look at the submit time for that message
If your archiving window kicks off at something like midnight, and it has a submit time of 2am, then it simply means that it re-queued the user for archiving but then ran out of time to get to that mailbox again.
So the way that it works is you have Number of Messages Per Pass set on the task, by default 1000 messages.....
1. The Schedule starts at midnight
2. Posts a message to A5 to Process Exchange Server
3. EV looks up all the enabled users for that exchange server
4. Posts a message in the queue for each enabled user
5. Each of those messages will have a submit time of midnight
6. EV will then take several at a time (default is 5 users or 5 concurrent connection)
7. EV then scans the mailbox and archives up to 1000 messages
8. EV then moves on to the next mailbox in the queue and so on and so forth until the queue is empty
9. Any mailboxes with more items to archive past those 1000 items will be re-added to the A5 queue
10. So if it took 1 hour to process all mailboxes at 1000 messages per pass, you may have additional mailboxes queued, and the submit time be somethng like 3:50am
Then your archiving schedule stops at 4am
Well the message is still in the A5 queue, because EV only had ten minutes to attempt to get to that mailbox and simply ran out of time
The A6 queue would be Moved/Updated Shortcut processing, and that will run throughout the day regardless of schedule to update the metadata in the ev database, so although you might come in in the morning and see 3000 messages in A6 queue, it will go down throughout the day.
Storage Archive and Storage Restore queues will also go down regardless of the schedule.
I believe A1 and A2 will still go down regardless of the schedule.....
None of the queues will move though if EV is in backup mode