Number Wizard error

So, I was testing my number wizard Ui code and I find a error.
This is my code:

 // Use this for initialization
    void Start()
    {
        NextGuess();
    }

    void StartGame()
    {
       
    }

    public void OnPressHigher()
    {
        min = guess+1;
        NextGuess();
    }

    public void OnPressLower()
    {
       max = guess-1;
       NextGuess();
    }

    void NextGuess()
    {
        guess = Random.Range(min, max + 1);
        guessText.text = guess.ToString();
    }
}

When I click on lower or higher button my max and min goes crazy. It keeps adding +1 or subtracting -1. It never stops…
I was acting like a user, so I found this error, how to fix it?

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