By default, a ghost of each Grease Pencil sketch displays before and after the actual frame. When working with a sequence of Grease Pencil frames, you can adjust how the ghost images display to change how the images blend together during playback.
To toggle ghost frames on and off
To change how long ghost frames display
(Select 1, 2, 3, 4 frames, or Other to enter a custom value, up to a maximum of 10.)