I believe you can take UTC, subtract (or add) your normal time zone hours, and then add 1 to it (for some reason, I'm UTC-6 hours (U.S. Central time zone), but in the manual it states that my time zone is zone 7).
Surprised it's 6. By similarity, I'd have guessed like 10. Saipan is listed as 8, which from the declination map (15N, 145E) has it on the 0 degree line, which corresponds to the compass code of 8. Looks like a reasonable rule of thumb is code = 8 - (dec/4)
It may be 8, there was no distinct movement between 5 to 8 compared to the higher and lower numbers so my choice was 6 or 7 to hit the medium, I just chose 6 because it is a sexier number than 7. the curves and all.