So then you can process it. Size of frame may be different from size of background. SubFrames can't be modified directly by user. They are always computed by mvCM according to next and previous frame. SubFrames command can be switched on or off.
Curves always uses background's palette.
The numbers are very important, because they are used for calculating in subframes. Each curve has own layer number. New curve will have color same as actual color. If you'll use right mouse button on drawing area while 'add' command is active, then active color is set to same color, where you pressed. In line bellow is automaticaly created list of selected curves.