Does it make sense to copy the route for a preliminary or subsequent leg?

What causes this issue?

You have set the leg indicator to preliminary or subsequent leg in the
transport type as well as selection the option for copying the routes
from the delivery into the shipment.

System Response

The system issues a warning. This is because there is little point in
copying the route for preliminary or subsequent leg. It is more
efficient to carry out a leg determination, which guarantees that the
shipment legs will be linked to the main leg shipment (for the main leg
shipment however, we strongly recommend that you do copy the route from
the delvery).

How to fix this error?

If you still want to copy the route here, ignore this message.

Error message extract from SAP system. Copyright SAP SE.