Minecraft wiki entry for Spawn, associated text: The population control caps limit how many mobs of each type and category can spawn within a 9 chunk by 9 chunk square region surrounding the chunk in which the spawn attempt is made. Mobs in chunks outside a ticking area still count toward population control counts as long as they were previously loaded (i.e. within simulation distance at some time) after relogging. The population control caps are split up into two distinct categories: a cap for surface mobs, and a cap for cave mobs. Cave mobs do not count toward the surface mob cap, and surface mobs do not count toward the cave mob cap. Whether a mob counts as a surface mob or a cave mob is determined by where or how it spawned, not where it happens to be at the moment. For cluster spawns, those that spawn on the highest spawnable block at a given coordinate count toward the surface cap, and any that spawn below the highest solid or non-solid but spawnable (e.g. ice or upper slab with air above) block count toward the cave cap. Structure-spawned mobs and converted mobs (i.e. drowned converted from zombies, witches from villagers, zombified piglins from pigs, and medium and small slimes from killed larger slimes) always count toward the cave cap, and spawner-spawned mobs always count toward the surface cap.