Dembski seems to be using a quantitive approach to demonstrate that novel biostructures could not have arisen as a result of either chance (or rather, that the improbability is such that it is as good as impossilbe [he multiples the number of quarks in the cosmos by the number of plank moments or something like that to get the denominator for the inverse of his threshold of so-improbable-that-it-is-as-good-as-impossible) or necessity. He concludes that these forms have arisen as a result of specified complexity. But the specified in this term is another name for something that a rational being, especially an engineer, would think of. So it's kind of a way of talking about teleology via quantification.