Any Fake data you have?
I can't share unfortunately.
It sounds like you need an "independent date" to hang your events on. I would suggest the following:
Create a "calendar" data source (either by listing out all the days in your range in a single column in Excel, or by using a system calendar in your DBMS if available).
Then duplicate your data source. Join one of them to your calendar using Date Shipped and the other using Date Returned. You can then get Quantity Shipped from one and the Quantity Returned from the other to create your calculation based on the Calendar's date.