Diagnosis
The weight unit in the delivery header is valid for the gross weight aswell as the net weight.

System Response
If you make manual changes to the weight unit in delivery change modeof the overview screens, the net weight is automatically converted tothe new weight unit.
However, if you create an outbound delivery without order reference,the net weight cannot be converted to the new weight unit if the weightunit was changed manually. In such a situation, the net weight could beincorrect. There is no check to make sure the net weight is less thanthe gross weight.

Procedure
Check the weights in the details view of the delivery header.