Dell P2724DEB User Manual page 52

3. Go to System Settings
4. In the drop-down menu of When I press the power button, there are a few
options for selection namely Do nothing/Sleep/Hibernate/Shut down, and
you can select Sleep/Hibernate/Shut down.
NOTE: Do not select Do nothing, otherwise monitor power button cannot
sync with PC system power state.
52 | Setting up the monitor