Project Manufacturing - Production Number

If we have both type of demand (Forecast and Sales order) how to handle this using Production Number? As per Project Manufacturing implementation guide,  it says that we can have any one type of demand with same production number either Forecast or Sales order. If we try to create a sales order with Production number and for same production number if Forecast exist then system does not allow to create Sales order.

If we use forecast as a demand, then at a later stage after production process for dispatch of material we need to have a sales order. So at that point whether system will allow to create Sales order with same Production number?