Peak vs average
A peak can be a short event, while the average shows the broader baseline. MineTracker shows both because a server with one huge spike may not feel as active as a server with a steady daily population.
Daily and weekly rhythms
Minecraft communities often follow school, work and weekend rhythms. Heatmaps and range controls help reveal whether a server peaks at predictable times.
Comparing servers by peak behavior
Two servers with the same current player count may have very different histories. Comparing peak time, average players and uptime gives a more complete view.