You have to understand these stats and their limitation before relying on them.
The number of cameras is irrelevant. Its the MP/s that matter. Yes there are 28 cameras however, if for example, they are running at 15fps (a guess) they are a mix of 2mp and 1mp cameras. If you tried the same with 28 4k cameras at 15fps that system would not handle it.
Another very important stat that is missing is whether limit decoding is being used. If it is used then you would see a fraction of the cpu usage vs not using limit decoding.