Octane retard works the same for L1, L6 and L8, all via pins 13 and 14.
When activated retard is 2, 4 or 8 degrees on standard program.
You get 8 degrees retard if you ground both pin 13 and 14.
You get 2 or 4 degrees retard by grounding pin 13 or 14. Check with a timing light.
You can ground the pins with running engine and then observe the timing change.