You likely entered some number of months less than 7 (6 or less is less than half the year) for how long the child lived with you.  Children at college are "temporarily away" from home and are still considered to live "with you" if they would be living wth you if not for college and it is reasonable to expect them to come home (at least for a while) after college.

On the other hand, if your child has established a permanent new home, then they don't live with you any more and can't be a dependent.  There is no black letter rule, each situation is determined by its own facts.

And, as mentioned, the child can't provide more than half its own support.  

If you got the $4050 question, you must have answered that the child did not live with you.  Otherwise that question won't come up.