Information on scorch marks

[u/Educational-Cat-5807]

Did a training burn last night, and went back this morning to check out the damage and see if i could learn anything about post-fire investigation before we do the final burn later today. The box we built was about 10 feet long, 5 wide, and 4 tall. Half of it was a sealed compartment, the other half was closed in by 2 walls and a ceiling. I think I understand why the scorch marks formed like they did, but can anyone give me a in-depth explanation by looking at the burn patterns, and tell me more about the science of it? Videos and photos attached.