It does not sound like the usual representation of a last supper. And I'm only guessing, but it almost sounds like a Masonic reference, with no link in my mind to the really stupid movie and book-- "The Da Vinci Code" (stupid from a factual and historical perspective).
Anyway, the numbers might also be references to texts in the Bible...? It doesn't sound like typical Christian iconography (symbolism). You'd have to post some photos somewhere, say how it came into your possession, and give some description of the visual acuity of your own naked eyes before any one could get a good idea of where you are coming from in relation to the picture. Good luck. -- Jabbahdah.