Based on the above the audio cable for Digirig will look like this:
DIN8 pin 1 (Transmit data) → 3.5mm TRRS ring 1 (RIG_AFIN)
DIN8 pin 2 (GND) → 3.5mm TRRS sleeve (GND)
DIN8 pin 3 (PTT) → 3.5mm TRRS ring 2 (RIG_PTT)
DIN8 pin 4 (Receive data) → 3.5mm TRRS tip (RIG_AFOUT)