Level 2, Sprint 3- 3.3.6 Activity: Test the Shipping Cost Formulas

Hi,

I am struggling with updating the formulas of Confirmed PO Delivery and Confirmed Purchase order receipt.

Regarding "Confirmed PO Delivery", I understand to replace OFFSET by POST, to push the data to future periods instead of pulling: POST(PO Submitted, -Final Shipping Time Weeks, 0).

But I don't get what is wrong with the formula of "Confirmed Purchase Order Receipt". Why should you replace OFFSET by POST?

In my opinion, the use of OFFSET is correct: when in a certain week the Confirmed PO Delivery is set to true, you have to look back in time which shipping amount was set?

By using POST in the formula you will look at certain point in time (EG week 3 FY20) to the confirmed PO Delivery, when it is "1" (because PO was submitted in week 1), the final shipment amount of week 3 (0) will be pushed to week 5 because there is a final shipping time of 2 weeks in Week 3. But, the purpose is to have the value of 1214 as "Confirmed Purchase Order Receipt" in week 3 as it is the final shipment amount in week 1. However, when using formula 
IF Confirmed PO Delivery > 0 THEN POST(Final Shipping Amount, -Final Shipping Time Weeks, 0) ELSE 0 

the value of 1214 (final shipment amount) will not be pushed to week 3 as the value of confirmed PO delivery is 0 in week 1.

What is the correct formula for confirmed purchase order receipt? Or am I interpreting the formulas in the wrong way?

Thanks in advance!