Inside the Immortal Building, there were several surveillance cameras on each floor. From the corridor to the elevator to the emergency exit, surveillance cameras were in operation. Added up, at least, a few hundred cameras operated in the entire building!
However, the size of the surveillance screen in the security room was limited. The image recorded by each surveillance camera at every moment could not obviously be displayed on the computer screen of the security room.
Because the size of the computer screen in the security room was limited, only twelve cameras could be displayed at the same time for real-time monitoring. That is to say, although there were dozens of times the number of cameras working, they were not all displayed on the security screen of the security room.