"Stop" if Door Recently Opened (Node Red)

I found a very clever Node red flow created by /u/Wwalltt which can be found here.

One of his flow’s checks to see if exterior doors were recently opened, and if SO, it will NOT notify you of camera motion. This is very useful because of the annoying things about camera notifications is the unnecessary ones such as when you’re stepping out to grab your mail or a package.

My question is, how does this specific flow work? I can’t figure it out although the code is all there. It uses subflows, node history, checks all the exterior doors of the house to see if they were recently opened. I copied this flow over into my setup and it was working flawlessly for a while, but I’ve run into issues now where its only checking one of the 4 doors I have listed in the flow.

Here’s the flow of the specific node