Numbered Dream (please help)?

I had a dream (but i think i might have been astral projecting on a subconscious level) that i was being chased by what i can only think of as a spirit. It could have been an alien or a creature from another dimension i don't know but it seemed like a spirit to me. It had a companion with it that Im guessing was a dog and it chased me around in this crazy looking field. After a while i just stopped running and asked him. What are you chasing me for? It said something like, I can't help but chase you, you're a unique one number 813.The numbers '813' appeared on the back of my neck. It told me it was in reference to E3. Then my dream showed me the number E3 in some book. I can't remember what was on those pages though. If anyone can possible help me understand this dream please do.