The same wrong number was in six files and I still don't know where it came from

Full disclosure before the story: I never found the origin. The correction I ended up shipping says "this number does not reproduce from the source", which is a weaker claim than "here is the bug that produced it", and I'd rather admit that than pretend the case is closed. The number is 1,803. A work order in my planning tree said a file ledger...