National Treasure

I've been wanting to discuss this topic.. Last month, I watched the movie, National Treasure Book of Secret. When I watched the ad clips, I just couldn't resist to watch it. It was a well researched movie. The movie is about Treasure hunter Benjamin Franklin Gates (Cage) looks to discover the truth behind the assassination of Abraham Lincoln, by uncovering the mystery within the 18 pages missing from assassin John Wilkes Booth's diary. FYI, the diary does exist.

I enjoyed the movie... but... I can't quite stop thinking about one particular scene. ( If you haven't seen the movie, go watch it, it's worth it) The first part of the movie reveals the story of the John Wilkes Booth's diary. In one scene, 18 pages were torn from the book and then got thrown into the fire, but luckily, 1 page was saved before it got completely destroy in the fire. The paper had a burnt edge due to the fire...

In later scene, when they tried to prove the genuinenity of the paper, they attached the paper to the torn book. It matched Now, my question is, how can the burnt edge has the same lenght, size, shape with the remaining torn edge?