Reguisition worksheet wants to set order date in the past

Hi.
I am trying to help a customer who want's to start using lead time calculation on their vendors in order to get a correct planned receipt date for purchase.

They are getting sales orders from a web shop with shipment date equal to order date. They run the requisition worksheet on daily basis but the problem when adding lead time calculation to the vendor is that the requisition worksheet suggest an order date in the past. I would rather see that the planned receipt date was set forward with as many days as the lead time calculation (with concideration to any base calenders).

Is there a solvation to this or how am I supposed to work with these dates?
Best regards,
Rebecka