This is the concept of median of statistical data, given that Mary was the 13th highest and the 13th lowest in the spelling contest it implies that the number of people was distributed as follows; 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25 This implies that since the median of 25 is 13, then the total number of people in the contest was 25
when you get to 0 at 7660 you round with the number next to it if its 5 or bigger you add a one to the number since 4 isn't greater than or equal to 5 than your numbers stay the same
