The OP is very inquisitive and really wants to know how these things work, etc. I think that we all wonder how this stuff gets programed into the system and there is certainly no harm in asking.

After awhile however, I kinda gave up trying to figure out what was going on and that was about 30 plus years ago when I stopped non-reving. I really lost interest 18 years ago when I first made 1K and ALWAYS had a seat assignment that I wasn't afraid of losing to practically anyone else on the plane.

The ONLY thing that a 1K needs to fear is being late to the gate, and getting screwed out of their meal choice. Upgrades are a perk and if I get a CPU I'm happy, if not 7F, with lots-a leg room works just fine!

How many people are left at the gate and/or how many open seats there are when the door closes is something that ain't in my job description, but that just me!

As long as I've got my seat, I really don't care about every flight, every day that UA fly's, or even the one that I'm riding on for that matter.