For instance:
Invoicing days: 10 and 20; delivery date: 15/04/2014 -> invoicing date: 20/04/2014; delivery date: 25/04/2014 -> invoicing date: 10/05/2014.
These fields only have impact on the cash forecast generation base on Sage X3 documents (see the functionCash forecast generation
You can fill these fields provided that the type of forecast is linked to a customer (or revenue).