An eight-frame animation does not have a fixed duration. At 8 fps it lasts one second; at 12 fps it lasts two-thirds of a second; at 16 fps it lasts half a second. Before drawing or generating more frames, check whether the problem is missing poses or the time each pose stays on screen.
Source: [Dev.to](https://dev.to/framesprite/stop-changing-your-sprite-sheet-to-fix-animation-speed-2ohf)