The basic information about surface warship specifications isn't classified. We know how many interceptor missiles they can carry. Standard doctrine is to fire at least two interceptors at each incoming threat in order to increase the probability of a kill. And empirically these defensive systems work very well, but ships in action empty their magazines quickly and then are out of action until they can return to a friendly base to rearm. At some point there just aren't enough hulls and missiles to sustain the effort.