The scale ranges from 1 (completely straight) to 10 (completely gay), with bisexual ranging from 5-6, depending on preference. Michael often notes that full 1's and 10's are particularly rare.
The numbers are as follows:
1 - Completely straight: only ever enjoyed porn with just singular women in it, or lesbians. If you've ever seen a man naked while erect, you are immediately bumped up to a...
2 - Mostly straight: has enjoyed porn with naked men in it , even though the main focus of the viewer was on the woman in the porn
(2.5 - Pretty straight: has enjoyed porn with mostly-female hermaphrodites in it)
3 - Moderately straight: has enjoyed porn with mostly-female transexuals (people born men, but surgically and often hormonally altered to resemble women) in it
4 - Slightly straight: has enjoyed porn with mostly-convincing transvestites (men who only dress like women, but have not had surgery or hormones to resemble them) in it
truncated for length