This is not a mistake. You misunderstood the rules. It's a '1SBI Share' which stands for 1 @steembasicincome share'. You can read my more detailed explanation in my other reply to your comment https://steemit.com/contest/@jamezz/re-alkasai-contest-steem-basic-income-1-free-share--2018-10-30-01-51-18-20181103t011449316z#comments
Let me know if you have any questions.