However, a special PACKET table is to be included in the header which indicates how many objects of each Packet are contained in the SDNF file. Any system importing the file is able to give some progress feedback as it knows how many items are expected without having to read the whole file at the beginning.
If the input SDNF file has the STARTTABLE header that lists the contents of the subsequent packets, the Import window Packet check boxes are (de)activated accordingly. If there is not this STARTTABLE block that defines the packets contained therein, all check boxes become active and you must select which packets to import.