If tens of thousands of people in the world can dance better than you, then let's assume the maximum number of "tens of thousands" before hitting "hundreds of thousands" -- 99999. Let's assume there are 7 billion people on Earth (not perfect, but good enough for back-of-the-napkin). That means you are (1-99999/7000000000)*100th percentile at dancing: 99.9986th percentile.

If tens of thousands of people in the world are better than you at dancing, you're a really good dancer.