there are 12 wards and 12 sub-wards on each of the 4 housing districts. in each ward and subward of every housing district is one apartment building. (12 + 12) x 4 = 96. so there are 96 apartment buildings in the game. each apartment building can hold up to 90 apartments. 96 x 90 = 8640. so there are 8640 apartments on every server.