Those numbers on the gas regulator are just like christmas ornaments. They are there for decoration and thats it. Just pretend that they don't exist and adjust the gas so that the rifle functions correctly.
You should reconsider using white box ammo only. Now, if you are filthy rich, then by all means, have at it. If you aren't filthy rich, then buy a few cases of South African surplus 308 and take that F A L to the range reglarly.