The process of selective perception is how an individual screens out non-relevant information. This screening process allows the user to concentrate or focus on signals that provide the information sought. If you consider working storage as a filter, then once information passes through the filter it enters Working Memory. This stage of the model serves as both temporary storage and a place for conscious thought to be pondered by the learner. The learner's previously learned experiences can be compared with the new information to determine the feasibility of permanently retaining the information for future recall.
Information resides here for as little as twenty seconds unless rehearsed by the learner.
I believe that, with a consensus effort and rehearsal, and possibly geographically picturing area codes in one's mind to aid this process, successful encoding can occur. Chunking data is key to learning expanded numbers. If meaningful encoding does not take place we can say that learning did not occur. You will recall that the encoding process occurs in working storage. With this limitation in mind, instructional materials should be chunked into sets of data that can be accommodated by Working Memory.