If you are following the instructions from Level 2 document it asks you to pick up Suggested Order Amount for the Month initially and later when you create an override line item it asks you to replace Suggested Order Amount for the Month with Final Shipment Amount. Your second last formula is somewhat close but not right
It should be IF Confirmed PO Delivery > 0 and not <=0 because maximum times it will be > 0
In POST syntax first parameter should be Final Shipment Amount & not Suggested Order Amount for the Month
In POST syntax second parameter should be Final Shipping Time Weeks
Can you please explain your sentence "It should be IF Confirmed PO Delivery > 0 and not <=0 because maximum times it will be > 0". I do not understand why you state the maximum times it will be greater than 0. If an order is placed when needed, according to the Reorder Flag, an order is only placed 1 or 2 weeks of the 4-5 week month, so there are more instances where an order is not placed, resulting in a zero. Wouldn't the best practice be "IF Confirmed PO Delivery = 0 THEN 0 ELSE ..."