What does the number of public rental housing in Shanghai represent?

The serial number of public rental housing in Shanghai represents the district and county number, building number and room number to which the public rental housing belongs. Specifically, the first two digits represent the area code, the middle four digits represent the building number and the last two digits represent the room number. For example, the serial number of public rental housing is "X 123456", where "X" represents the code of Shanghai, "12" represents the district and county number to which the public rental housing belongs, and "3456" represents the building number of the public rental housing.