Help me in solving BMCP12 problem

My issue

while (t–) why this is used in the code ?and what is the meaning of this(–) sign?

My code

// Debug the following Code

#include <stdio.h>

int main() {
    int t;
    scanf("%d", &t);

    while (t--) {
        int X, N, points_per_testcase, score;
        scanf("%d%d",&X, &N);

        points_per_testcase = X / 10;
        score = points_per_testcase * N;

        printf("%d\n", score);

    return 0;

Learning course: C for problem solving - 1
Problem Link: CodeChef: Practical coding for everyone

Here t variable inputs the no of test cases required.
while(t–) executes the code inside the loop t times.
Here (t–) decreases the value of t by 1 after every loop execution.
When t becomes 0 the while loop breaks.