That is the viewable screen real estate on that display.

Look down on right...

Technical Specifications

Screen size: 24 inches (diagonal viewable)
Screen type: TFT active-matrix LCD
Resolution: 1920 by 1200 pixels
Colors: 16.7 million
Viewing angle: 178° horizontal; 178° vertical
Brightness: 330 cd/m2
Contrast ratio: 1000:1

A society grows great when old men plant trees whose shade they know they shall never sit in.