The settlement index is designed to take an average price on the day your option expires. Since you are either 'in-the-money' or 'out-of-the-money' by 1 cent either way, they had to use an average:
http://www.tradeingroups.com/understanding-fixed-return-options-fros/
http://www.tradeingroups.com/understanding-fixed-return-options-fros/