The Thumbnails window uses these options to determine how to split the graphics into thumbnails:
Memory Preset commands: When selected this option will generate a new thumbnail each time a Memory Preset command is reached. This command is used to clear the graphics and hence makes a good option for dividing thumbnails. The downside is that not all manufacturers utilize the Memory Preset command.
Timing Gaps of at least: When this option is selected CDGFix 3 Super will generate a new thumbnail for each graphics "silence" of at least the entered number of seconds. This method is less accurate but can give a reasonable thumbnails division with the default 3 seconds gap.
For more details of the graphics instructions please refer to The CDG graphics format.