The description for the generalist badge says:
Provided non-wiki answers of 15 total score in 20 of top 40 tags
How do we know what the top 40 tags are? There is a display of 25 tags on the page, but I am unsure if they are taken from the top 40. Also, I am going to assume that the score (saying total) can be gathered through several questions (i.e. if I answer a question 15 times and only get 1 point each time, that would still count).