A parcel service can use a productcode to indicate the requested treatment of a shipment to be sent. At Post NL for example, delivery product code 3085 means a regular 'normal' shipment. A shop has to sign a contract in wich they will agree about the possibly productcodes that they are allowed to use.
Please keep in mind that we can't help on the productcodes used by each parcel service partner. Contact them directly to get information about the codes being used.