The Order Preparation Days Preference enables the automatic calculation of the days between the Scheduled Pick Date and Promised Ship Date, on the sales order detail line. Promised Ship Dates are updated based on the Promised Delivery Dates and the “transit days” and/or “lead days” specified on the routing for the load’s routing option.
Hence, in a transportation sales order, the dates are recalculated depending on the shipment, route and load setup.
If the Order Preparation Days (16) Basic Preference is activated and "Lead Days" and "Transit Days" are blank in the route, then the transportation setup will not overwrite the dates in the transportation sales order, when the shipment is
routed. This is a case when the transportation sales order dates established by Order Preparation Days Preference (16), will not be changed and this preference works with Transportation .
More information and examples can be found in the following KM documents :