As the list scrolls horizontally until the last column is totally visible, there is usually a blank area between the last column and the right border of the list.

The color of this blank area depends on the setting of the DeadAreaBackColor property. You can eliminate this blank area with the ExtendRightColumn property. The default value of this property is False, but if you set it to True, then the last column will extend its width to the right edge of the list.