The airline who said to erase the entry is incorrect. Some States have a procedure to issue import approvals for certain commodities. Such requirements May not be included in their State Variations. There will be a need to indicate such reference numbers in the Authorization column or the Additional Handling Information box of the DGD. The DGD is a communication document to advise all concerned of the nature and references of the dangerous goods being carried on the aircraft.
While it is not permitted to show entries that do not relate to the dangerous goods being shipped, there is nothing against entering information which May be vital or relevant to the dangerous goods being carried.