The ## symbol stands for Van's AV-50000A.
On the AV-50000A are several connectors. The headset uses the intercom and optional connectors on the AV-50000A. So OPT 28## represents pin 28 of the optional connector on the AV-50000A. Likewise, INT 11## represents pin 11 of the intercom connector on the AV-50000A.
The ES-00147 Headset module has a 12 pin connector. Pins 3, 4, and 8 are
for the headphone. Pins 2 and 5 are for the mic.
The wire numbers on Van's electrical drawing are actually part numbers.
While most of them are unique, some wire part numbers could be used in more than one circuit if they happen to be the same color and length and wire size. 2CS stands for two conductor shielded cable. That is followed by
the AWG wire size, for instance 22. The last number is the length in
inches, for instance 31 inches.