Dell S2230MX Monitor - Manual (Page 31)

If an image appears to be stuck on the monitor, select LCD Conditioning to help eliminate any image retention. Using the LCD
Conditioning feature may take some time. LCD Conditioning feature cannot remove severe cases of image retention or burn-in.
NOTE: Use LCD Conditioning only when you experience a problem with image retention.
The below warning message appears once user selects “Enable" LCD Conditioning.