The maximum amount of data that will be moved into the target mailbox. For example, if you specify "500MB" then content will ...

The maximum amount of data that will be moved into the target mailbox. For example, if you specify "500MB" then content will be moved until either there is no more content to move or the mailbox contains 524288000 bytes of data. At the end of the migration, the target mailbox should be not more than approximately 500 megabytes (MB) full. If the target mailbox is smaller than the specified value, the move stops when the mailbox is full.