Elantra2.001 told me the numbers on the head of the bolt simply identifies the "hardness of the bolt." So, a 4 is pretty weak I guess, and that's probably why you broke it. First just hand tighten them, then give them a couple good turns with a wrench and you should be set.
One example I can think of the proper reason for torqueing, is an intake manifold. Mos intake manifolds have 6 to 10 bolts that fasten it to a motor. The intake manifold must have a good seal and the means that the plane of the intake has to be completely flat. If one bolt is tighten more than another the mating surface of the intake will bend causing gaps and leaks.
Or any critical part. On the dash, use common sense. If you are going into plastic, it probably doesn't need to be super tight. If you are boing into metal, it can probably be a little tighter. Just remember, use common sense when you are working with interior parts.