That can't be right! Add % for number 1 and number 16. What do you get? Now add the rest. I think the question is yet to be answered.
It is confusing, but I think it is the percentage of people who voted for it. Keep in mind this is a multiple choice poll.
Look at #1 with 140 votes, at basically 50%. 280 people have voted. So the percentage is showing that half the people who have voted have included #1 in their vote.