Samsung LS23MUQHB-ZA - Manual (Page 18)

2-3 Installing the Product
3. Specifying the Monitor Number
The monitor number is set to 0 by default.
A monitor can be controlled by the multi-control pad even if the monitor number is not specified.
1. Press the [MONITOR SELECTION] button on the back of the monitor to specify the monitor number.
(Range: 1 - 6)
2. To control the monitor you want, press the monitor number below MONITOR SELECTION on the multi-control pad.
To control all of the connected monitors, press SELECT ALL on the multi-control pad.