If you want to transfer this item you pick the serial number and move it.
If however you realise the serial number was created incorrectly and should have been ABC1234 you use a reclassification journal to set the new serial number - no other reclassification fields require alteration to change the serial number.
Yes the reclassification journal is how you change the serial number, it is not possible to change the serial number through a transfer order and the new serial and new lot number fields are NOT editable as standard on a transfer order.