How is demand calculated for the seed queue

[LevitatingBusinessMan]

When talking about the seed queue the manual states:

The seeding queue does not use torrent_status::queue_position to determine which
torrent to seed. Instead, it estimates the demand for the torrent to be
seeded. A torrent with few other seeds and many downloaders is assumed to have a
higher demand of more seeds than one with many seeds and few downloaders.

How is this demand calculated when the tracker's aren't pinged when the torrent is idle? I noticed that when qbittorrent starts, it shifts all the seeds to an active slot until it has a seed/peer count for all of them. Only then will it choose high-demand seeds and stick with them.

Does it just calculate demand once and expect the amount of seeders/downloaders for a torrent never to change?