The realm list now shows populations based on peak population for the last 7 days, instead of real-time:
A few minutes ago, we enacted a change to how the populations are calculated in the WoW Classic realm list. Since shortly after the launch of WoW Classic, the realm list population labels have indicated real-time population levels.
Now, the Low/Medium/High/Full labels are based on peak population over the last 7 days. We believe this provides a more-useful picture of a realm’s population to players who are making decisions about which realm to play on or transfer to.
The realms which have not yet moved to one layer will continue to be marked “Layered”.
Thank you!
Source: https://eu.forums.blizzard.com/en/wow/t/realm-list-populations-updated-28-october/98659
Good stuff!
My "dead realm" is listed as "Full"!