Voting on 600 questions counts like the descriptions says.

But you should not only have that votes because you already voted on millions of posts and some of them were questions. 

It is a badge to award your voting on questions. That badge was introduced because people all the time vote on answers but often forget to vote on questions too.

That is why 25% of your votes should be on questions. Meaning you can only have a 75% vote on answers, not more. That is a second condition to make sure you have a fair share of voting for questions, not only for answers and a bit of questions.