Afterwards is the literal translation of the text. Energy Management is not an issue of quantity of the people managed, but your actions in managing them. Just because that sounds simple, does not mean that it is simple. Mastery of the simple can take as much time as mastery of the complex.
Energy is potential, like the cocking of a crossbow.
Decision is the action, like releasing of a trigger. Never let the opponent know what he is up against. Use your tools well, both the potential and the action. In all fighting, the direct method may be used for joining battle, but indirect methods will be needed in order to secure victory. There are not more than five musical notes, yet the combinations of these five give rise to more melodies than can ever be heard.