Number of threads. The number of threads that the task will use when processing mailboxes. You may find that increasing the number from the default (10) improves performance.

Maximum number of items per target per pass. The maximum number of items that are archived from each mailbox on each mailbox archiving pass. If there more time left in the schedule at the end of a pass through the mailboxes, the task continues processing from the beginning of its mailbox list.