In Tibia many monsters ("count") can be assigned to one square named home. When the home square is already occupied, next monsters look for a free square around, counter-clockwise (square '1' is home):

For each home there there is one timer, means monsters of the same home didn't spawn independently, but one after the other. Respawn depends on base home "regen", on players online number and partly on randomized number. For example, for base home regen = 600 (10 mins) when there are no players online it takes between 5 and 10 mins to respawn (7.5 on average). The more players online, the faster it gets, reaching the shortest time at 600 online, se respawn takes 2-4 mins (3 on average). Lower regen (rats under Al'Dee with 200-300 value) results in faster spawn, higher regen (monks in IotK monastery) results in longer spawn.