Main level (COA) status are defined by priority/most significant item status in this order: 6 - 8 - 1 - 2 - 3 - 4 - 5 - 9 ie. which is most important item action to take. 

Most important logic: ST1=6 appears some defined days before delivery, total goods amount is not in stock - ordered goods needs urgently followed up/chased. ST1=8 appears when shipping is possible due to partly or whole item quantity can be delivered according to the delivery date -DelDate- as well. Default is partly shipping allowed. 

If the customer order has the settings ‘handling the complete order/item activated, this will too have effect on the status. You can find these configurations in CUS Handlings 'Delivery on Complete Itm/Order-one or both.