What is a sub task in problem codes here?

help
1

As I was practising past contest problems, CodeChef: Practical coding for everyone
I encountered a statement against my first solution that is it’s completed 0%subtask,
and my code is wrong. Please help me know what’s wrong with my code?
CodeChef: Practical coding for everyone

2

@jade764
U have to keep summing up the previous rounds scores as well .
like to compute 3rd round u have to add score of 1,2 in the 3rd round then calculate it.