Dell P2815Q Monitor - Manual (Page 47)

Operating the Monitor
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47
OSD Messages
When the monitor does not support a particular resolution mode you will
see the following message:
This means that the monitor cannot synchronize with the signal that
it is receiving from the computer. See Monitor Specifications for the
horizontal and vertical frequency ranges addressable by this monitor.
When the Dynamic Contrast feature is enabled (in these preset modes:
Game or Movie), the manual brightness adjustment is disabled.