Using util.Random for dice roll but getting constant pattern

My assignment is supposed to simulate a running total of a dice sum depending on how many dice are used and how many rolls the user wants. The sample output shows that the percentage of each sum occurring varies a lot, however, the frequency of mine are all around the same percentage. I'm not sure how to fix this.

    package project1;
   import java.util.Scanner;

   import java.util.Random;

 public class DiceStats {

public static void main(String[] args) {

    int diceCount;
    int rolls;
    int min;
    int max;

    // Ask user how many dice 
    System.out.print("How many dice will constitute one roll? ");
    Scanner dice = new Scanner(System.in);
    diceCount=dice.nextInt(); //store it into diceCount

     min = diceCount; //minimum sum
     max = diceCount*6; //maximum sum

    int[] diceSum = new int[max+1]; //initialize array size

    System.out.print("How many rolls? ");

    //Ask user how many rolls 
    Scanner roll = new Scanner(System.in);
    rolls=roll.nextInt();

    Random sum= new Random(); //random sum generator

    System.out.printf("\n%s%10s%10s\n", "Sum", "     # of times", "     Percentage");

    //for loop to sum up # of times
    for (int i =1; i<= rolls; i++)
    {
        ++diceSum[sum.nextInt((max-min)+1)+min];
    }


    //for loop to print out: sum, # of times, and percentage    
    for (int i = min;i <= (diceSum.length-1); i++)
    {
        double percentage = (double)diceSum[i]/rolls;
        System.out.printf("%d          %d         %.2f%%\n", i,   diceSum[i],percentage*100);

    }


} 

}

This is how my program is being outputted: my output

EDIT: This is the sample output I am comparing mine to: sample output