The poll you made allows someone to pick more than one option. Any poll with the boxes & checkmarks is like that. The ones with the circle & the black dot in the center only let you pick one option. When you made it, you must've forgotten to specify that people were only allowed the one vote.
Aaaah, I see now But I didn't realize it , otherwise I would voted twice too Now it's too late, I think we can't vote again .