According to John Gardener, the distance is defined as the distance the reader feels between himself and events in the story. The psychic distance of the reader can cause any fact, temporal or spatial, as well as character traits from the story. In this sentence, the fact that could create a psychic distance is a "humble miller" in the case that the reader is not humble or is engaged in some other business, not a miller. What certainly creates the distance is the introductory part of the sentence "once upon a time", creating the distance that it happened long time ago in relation to the time in which the reader lives.