I want to display monitor A with 4 cameras & monitor B with only 3 cameras.
I am using a BNC T-joint to loop the DVR monitor display output to A & B monitor, but my aim is to have 4 cameras in A and only 3 cameras in B.
Is there any solution?

appreciate if anyone can have such solution to my aim. thanks

What will help if you tell us which DVR are you using? Some DVRs have what is called "Spot" outputs, that allows you to feed video and extend to different monitors...

If nothing else, then you can use two different video quads... basically take the looping outputs of each four ports, feed it to the quad and take the output of this video quad to a separate monitor...