Symbols whether they are pictures, letters, words or numbers have several functions but the most important is the gut level reaction to them, emotional or visual. For me they not only affect on an emotional level but can become part of the back ground without meaning but having a visual effect, they becomes like landscape, for instance the double X above the heads of the couple provides transition in color without taking meaning from the "x-rated" symbol. You feel that it is background rather than a rating for a movie. The number in this piece could be a reference to an address possibly a phone number, there are quite a few things linked to houses thru numbers. I use letters , words and numbers all the time in my work and they have an appeal to me because of the emotional aspect and also for their their physical appearance as well. Once in a while I want to guide the viewer in a new direction so I add a clue a word or a number.The clue is the word shadow at the top, referring to the "shadow ghosts" above the couples heads. Is it the previous owners? Did they have a happy life? Is it the spirit essence of the house? Who knows, but in old house I think we all understand the spirits of those who lived and died there remains forever as a part of the house.