A Time slice is the period between the last rendered frame and the current rendered frame. Think of Time slices as dynamic amounts of time. If a project is running at a consistent 60 FPS, then the time slices will be 1 frame in length. If a project is having trouble keeping up with real-time, and drops 10 frames, the corresponding time slice would be 10 frames in length.
Using the example above, when the timeline is running consistently at 30 FPS, every time slice is 1 frame in length. If there are two ramps going from 0 to 1 over the course of one second (30 frames), both outputs would be smooth ramps. If, for some bizarre reason, only every tenth frame was cooked, there would be very different results. In the non-time sliced CHOP, the value would jump every time a frame is cooked, while the data between those cooked frames is lost. The Time sliced CHOP is aware that it is only being cooked every tenth frame, and will cook the frames inbetween to interpolate between the value of the last cooked frame, and the current cooked frame. This keeps the data smooth no matter what is going on.