Dell UltraSharp 42.51" 4K Monitor - Manual (Page 40)

40 | Setting up the monitor
When the monitor and PC power state are both ON, while you press and hold 4
seconds on monitor power button , the screen prompt will ask if you would like to
shut down the PC.
Press and hold 4s
USB-C
Slide to shut down your PC
When the monitor and PC power state are both ON, while you press and hold 10
seconds on monitor power button , the PC will shut down.
PC will shut down Press and hold 10s
USB-C