i8kctl fan 1 1
-1 -1 (wrong)
i8kctl fan 0 0
1 1 (wrong)
i8kctl fan 2 2
2 2 (correct)
It's not just an off by one error, both 0 and 1 are wrong, while 2 is correct.
I did the set and waited several seconds for the fans to hit that speed before running the set again.