Sorry to make you confused.
Airfreight charges for both 1501-00-0006 & 1501-00-0014 are to be included in 1501-00-0006.
As for the export declaration charges, these only need to be charged once per shipment. It has already be included already in 1501-00-0014.
Hence you only need to revised your purchase order 1501-00-0006 to change the airfreight charges to EUR 740. The total for this purchase order will be EUR 2940.
Please let me know should you have any further questions.