It's 999 levels, unless I made a mistake somewhere (and if I did, please mention where you're getting the error, and post relevant files and logs). And you may want to consider only choosing levels others might reasonably want to play instead of including every level you can find. You can use the welcome message to give a link indicating what's on your Level List.

Keep in mind that the Anniversary Bash packs--which I suspect you might be including in your Level List--as a whole contain a lot of duplicate levels. And many of the Bash levels are old versions. I would strongly suggest using only the versions of the levels released by the original authors on J2O if this is at all possible as they tend to be the most up-to-date.