Codechef challenge problem

after the contest is over, which submission of the challenge problem will be considered for the final score ? the recently submitted solution or maximum score solution ?
and why is my challenge problem score is getting reduced for every few minutes ? is my score compared with all other’s solutions ?

solution in which you scored maximum points is considered. Yep if other get higher points than yours then your rank will be go down and he will move up. ex - if your score is 300 and rank is 4000 and if someone gets 310 score he will be promoted to some rank below 4000 and your rank will changed to something>4000