Coverage

No tracker sees every account. Wargaming's API is rate limited, so a site discovers accounts through clan rosters and searches, then refreshes each on a cadence it can afford. Coverage is the share of the region's active players it holds, and how recently each was updated.

It matters because every leaderboard and every server average is computed over the tracked population, not over the whole server. Wide coverage makes those numbers representative, thin coverage makes them a sample.