Same randomly generated integer repeats in while loop in c#

I'm creating a text-based game, and in the game when an enemy hits you, the amount of damage done is randomly generated, however, in a while loop it repeats the generated number.

Expected Outcome

Okay, lets fight him!
The monster has a health of 25! What do you wish to do?
[Press 0 to attack.]
0
The monster's health went down by 2. Their health is now 23
The monster attacks! Your health went down by 9. Your health is now 41
The monster has a health of 23! What do you wish to do?
[Press 0 to attack.]
0
The monster's health went down by 2. Their health is now 21
The monster attacks! Your health went down by 10. Your health is now 31
The monster has a health of 21! What do you wish to do?
[Press 0 to attack.]

Output

Okay, lets fight him!
The monster has a health of 25! What do you wish to do?
[Press 0 to attack.]
0
The monster's health went down by 2. Their health is now 23
The monster attacks! Your health went down by 3. Your health is now 47
The monster has a health of 23! What do you wish to do?
[Press 0 to attack.]
0
The monster's health went down by 2. Their health is now 21
The monster attacks! Your health went down by 3. Your health is now 44
The monster has a health of 21! What do you wish to do?
[Press 0 to attack.]

You can see that in the output the amount of damage the enemy does is repeated. Why is it doing this and how do I fix it?

Code:

using System;
using Game;

public class Zero
{
    public static void G1()
    {

        while (Player.HP > 0||Enemy.h > 0)
        {
            Console.WriteLine($"The monster has a health of {Enemy.h}! What do you wish to do?");
            Console.WriteLine("[Press 0 to attack.]");
            string read_action = Console.ReadLine();
            if (read_action == "0")
            {
                Enemy.h = Enemy.h - Player.At;
                Player.HP = Player.HP - Enemy.at;
                Console.WriteLine($"The monster's health went down by {Player.At}. Their health is now {Enemy.h}");
                Console.WriteLine($"The monster attacks! Your health went down by {Enemy.at}. Your health is now {Player.HP}");

            }
        }



    }
}

Variables that were in another file:

 public static Random numGen = new Random();
 public static int at = numGen.Next(1, 11); //this is the enemy's attack function