The number in ( ) is something called "reputation". Everyone starts with 25, but as you get upvotes from high reputation users your reputation will increase. However, if you will be downvoted by higher reputation users, your reputation decreases.

Generally, anything better than 25 is considered good and if you drop below 25, it's usually bad. At 0 or below your posts will be "hidden" (people can still see them if they want), but this is mostly meant to hide comments/posts from spammers.

Hope that answers your question about the numbers between ( ) :)