I think the point is, out of those claiming to be straight, 10% are engaging in homosexual activities. That is a separate figure from the 10% of the population that claims to be gay.
Interesting psych study: those claiming to have the highest disgust regarding homosexuality showed the highest levels of physical arousal when shown homosexual pornography. That is to say, if you are a big ol' gay basher, chances are that you are sexually aroused by gay sex.
I ain't no queer or nothin...