Analyzing Appendix A

I've wanted to do a deep dive into the AD&D DMG's Appendix A for a while, but have struggled to get started because this section of the DMG is really difficult to wrap my head around. How could I write effectively about something I did not understand?Time and again, I broke out my graph paper, my pencil, my dice, and my handy DMG to randomly generate a dungeon using Appendix A. I was always very quickly confounded by the sprawling complex of rooms, chambers, and passages that stretched out in all directions at once, twisting and turning out towards the edges of the page and then unexpectedly back in on itself to bump up against where I had started.It was nonsensical and confusing. What table am I supposed to roll on, and when? What is the difference between a room and a chamber? Why are there so many diagonal passages? Just when I thought I was done with my dungeon, I'd randomly roll up a set of stairs down one level, then a trap door in a corridor which drops the player characters…