Have you tried the retime option. It simply squeezes or expands the keyframing so the entire animation either plays faster or slower. If you move your keyframes closer you will get your entire animation in 64 frames but it will play faster ,If you change frame rate from 30 to 20 it will play in the same time. Fewer frames may give you jerkier movements. Also: delete keyframe deletes the keyframe from the animation. However when you run the animation that frame is interpolated and may well seem identicle.