Exaggeration is about really pushing your characters, actions and drawings way beyond reality. This can be for several frames, to put extra emphasis on a motion, or it could be for a hold, adding in comedic effect. Since there are no rules to what can be drawn on paper (or screen), you can break all boundaries set up by realistic expectations!
While you should aim to keep volumes consistent throughout your animation, it is totally okay to break them (or push them to exaggerated extremes) to further communicate the action you're animating.
Stay tuned for interactive demo animation!