There are 5 frames. The full cycle animation (all 5 frames) takes 10 seconds - 2 seconds each frame.
All frames are located in the slider container which is 500% (x5 of the demo block width). Each frame takes 20% of the container (100% demo block width), and is floated to the left. Thus, the 5 frames are located one after another from left to right in the container.
At the beginning the first frame is visible. While animating the slider is shifted left by -100%, showing the next frame. Note that the frame is stable for 20% of the 2 seconds and is shifted on the next 5% of the 2 seconds.
When the animation reachs the last frame, it jumps to the first frame and starts again (infinite animation). Last frame is identical to the first one, thus, the transition between the last and the first frame is not visible.