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  I have no idea of what the 4x version is doing with this --- I am unable to figure out what it is actually timing.

"Back in the day" of 3x, I used it for torrent management. Long periods of time with no activity was a pretty reasonable indication of zero interest in the particular torrent --- time to declutter by removing it. 

That's what I've come here to ask, too, so I hope someone knows! Since the update every item says its last activity was 18 hours and [some] minutes ago, regardless of when it was added or how much it's been seeding.