"One vote counts for a change." This line means the importance of each individual's voting=vote. To achieve/succeed on the French Revolution, France had implemented a very important election deciding for the king to give up his throne. In this=that election, some=the citizens who wanted to get a sovereign power won by just one more vote than the other citizens who wanted to keep the throne. In this=that context, we can know/realize the power of one vote. Just one vote can change the our society. Therefore, we muse=must vote on every election.