It's currently at 36. Last night 12 of them sang. From that group, the top guy & girl and then the next highest vote getter goes through (so 3.) The next 2 groups of 12 will sing the next 2 weeks. That will give us 9 of the top 12. The fourth week will be a "Wildcard" and the judges will pick 3 of those 12 to go on to the top 12.
I might be off on the Wildcard portion, but I know that's how they're getting the first 9.