Transgender people are already a very, very small minority. The number of people that are in favor of authoritarian communism is also quite low (certainly in the US, at least).

Couple things:

• They might each be small minorities of the overall population, but that doesn’t mean they don’t have a very large overlap with each other. Assuming that they don’t simply because you don’t personally know many who fit that intersection could just mean that you don’t frequent the same spaces they do - possibly because you don’t share one or either of those characteristics
• I’ll let you do your own math and get back to me if your calculated percentages could possibly add up to 700 people (half of an estimated 1400 monthly active users) on the internet who identify as both trans and communist