Auto Retry Count:
The Auto Retry Count parameter specifies the number of attempts to restart the migration batch to migrate mailboxes that encountered errors.

Incremental Syncs:
Incremental synchronization is enabled. Any new messages that are sent to the source mailbox are copied to the corresponding target mailbox once every 24 hours. This is the default value.

Auto Complete:
The AutoComplete switch forces the finalization of the individual mailboxes as soon as the mailbox has completed initial synchronization. You don't need to specify a value with this switch.

If you don't use this switch, you need to execute the “Complete Batch” button to finalize a migration batch.