Clear Button In Assign Channels To Pixel Plane

[injury]

Under the Pixel Plane Menu, Assign Channels To Pixel Plane. When I select a horizontal row and hit clear, it is clearing the vertical column of the number selected. So for instance if I drop down on the left and select row 16 to turn it green, hit clear column 16 is getting cleared instead.

Looks to be Version 24J (says it is the latest version)