User defined:The colorbar range is determined by the user. To define a range directly from the Colorbar active dialog, press the Ctrl key on your keyboard, and then click and drag out a new range on the colorbar. When you release your mouse button, the new range will be applied to your map. To turn off the user defined range, right click on the colorbar and select Automatic Range from the shortcut menu. You can also define a range from the Colorbar/Histogrampage in the Color Properties section of General Basemap Properties. 

Automatic: The colorbar range is determined from the minimum and maximum data values of all of the ribboned data that is being displayed, including data that is outside the current map view.

Window: The colorbar range is determine from the minimum and maximum data values of the ribboned values that are being displayed, and are visible in the current map view.