So a lot of the “full” and “high” individual servers are really just 1 single connected server that makes all realms connected to it also labeled as “full” or “high”
For example Alterec Mountains and Anvilmar both show as “full” but they are connected together along with 8 other servers. All 10 on that cluster show “full” for their own server, yet are all connected to each other. That’s 10 full servers that is really 1 server.
This is an old link likely out of date now showing retail only has 52 actual separate “servers” after all the connections plus a handful of realms that aren’t connected.