Help me in solving HS08TEST problem

My issue

I can’t understand this problem. Please help me.

My code

#include <iostream>
using namespace std;
int main()
{
    int x;
    float y;
    cin>>x;
    cin>>y;
    int r= x%5;
    float s= y-x-0.50;
    if(r==0&& y>=x-0.50) cout<<s<<endl;
    else cout<<y<<endl;
    return 0;
}

Problem Link: ATM Practice Coding Problem - CodeChef

@divya32997345
what did u not get in this problem?