Backtrack the difference between these two codes

Question

I have been trying to play around with backtracking. From my understanding these two codes are doing same thing but somehow I got different outcomes.

I am just trying to use some type of template to start with.

cout<<i<<endl;
backtrack(i+1);
backtrack(i+1);

and

for(int i=start; i<n; i++){
    cout<<i<<endl;
    backtrack(i+1);
}

The first one gets 5 as outcome and the second one gets six when I have the input of nums=[1,1,1,1,1] target = 3

public class Solution {
    int count = 0;
    
    public int findTargetSumWays(int[] nums, int S) {
        calculate(nums, 0, 0, S);
        return count;
    }
    
    public void calculate(int[] nums, int i, int sum, int S) {
        if (i == nums.length) {
            if (sum == S) {
                count++;
            }
        } else {
            calculate(nums, i + 1, sum + nums[i], S);
            calculate(nums, i + 1, sum - nums[i], S);
        }
    }
}

class Solution {
public:
    
    int count;
    
    void backtrack(vector<int>& nums, int target, int start, int sum){
        if(start==nums.size()){
            if(sum==target){
                count++;   
            } 
            return;
        }
        else{
           
            for(int i=start; i<nums.size(); i++){
                //sum+=nums[i];
                backtrack(nums, target, i+1, sum+nums[i]);
                sum-=nums[i];                     
            }               
        }
    }
    
    int findTargetSumWays(vector<int>& nums, int target) {
        count=0;
        int sum=0;
        int total=0;
        for(auto x:nums)total+=x;
        vector<vector<int>> dp;
        backtrack(nums, target, 0, sum);
        return count;
    }
};