Used as a power distribution point in my 1985 Carrera 3.2:
Starting at the top going clockwise:
R - 1 medium gauge yellow wire provides power to the radio - it is hot in all key positions except off.
15 - 1 large gauge red/black wire which Ys at a connector and then feeds fuse box 1 fuse 7 in powering several items. Powered in the RUN and START key positions.
50 - 1 large gauge yellow wire to power the starter solenoid. Powered only in the START key position.
P - 1 medium gauge gray wire provide power to the turn signal and headlight dimmer switch in the OFF key switch position only.
30 - 1 large gauge red wire that is the always hot feed from the battery into the switch. This is connected to a smaller gauge yellow/red wire to an inline fuse to the radio and a large red gauge wire to the light switch.
X - 2 large gauge wires - one is red/yellow which goes to fusebox 1 fuse 5 for heating controls and outside mirror circuits. The other is red/white and goes to position 75 on the light switch as the main power for the lights. This is powered with key switch in positions ON and RUN only.
30 - the other large gauge red wire through the bulkhead connector that is the always hot feed from the battery into the switch.
I hope this is useful and has not already been detailed. I apologize in advance if I have made any errors.