Towards the end of the bar being filled, I can click again. Does anyone know why?

c#
namespace FishingSharp
{
    public partial class Main_Menu : Form
    {
        private System.Windows.Forms.Timer cooldownTimer;
        private int cooldownDuration = 1000; 
        private int elapsedTime = 0;
        private bool Fishing = false;

        public Main_Menu()
        {
            InitializeComponent();
            InitializeCooldownTimer();
        }

        private void InitializeCooldownTimer()
        {
            cooldownTimer = new System.Windows.Forms.Timer();
            cooldownTimer.Interval = 20; 
            cooldownTimer.Tick += new EventHandler(CooldownTimer_Tick);
            Cooldown.Maximum = cooldownDuration / cooldownTimer.Interval;
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (!Fishing)
            {
                elapsedTime = 0;
                Cooldown.Value = 0;
                Fishing = true;
                cooldownTimer.Start();
            }
        }

        private void CooldownTimer_Tick(object sender, EventArgs e)
        {
            elapsedTime += cooldownTimer.Interval ;
            Cooldown.Value = elapsedTime / cooldownTimer.Interval;

            if (elapsedTime >= cooldownDuration)
            {
                cooldownTimer.Stop();
                Fishing = false;
                Cooldown.Value = Cooldown.Maximum;
            }
        }
    }
}

c#
namespace FishingSharp
{
    public partial class Main_Menu : Form
    {
        private System.Windows.Forms.Timer cooldownTimer;
        private int cooldownDuration = 1000; 
        private int elapsedTime = 0;
        private bool Fishing = false;

        public Main_Menu()
        {
            InitializeComponent();
            InitializeCooldownTimer();
        }

        private void InitializeCooldownTimer()
        {
            cooldownTimer = new System.Windows.Forms.Timer();
            cooldownTimer.Interval = 20; 
            cooldownTimer.Tick += new EventHandler(CooldownTimer_Tick);
            Cooldown.Maximum = cooldownDuration / cooldownTimer.Interval;
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (!Fishing)
            {
                elapsedTime = 0;
                Cooldown.Value = 0;
                Fishing = true;
                cooldownTimer.Start();
            }
        }

        private void CooldownTimer_Tick(object sender, EventArgs e)
        {
            elapsedTime += cooldownTimer.Interval ;
            Cooldown.Value = elapsedTime / cooldownTimer.Interval;

            if (elapsedTime >= cooldownDuration)
            {
                cooldownTimer.Stop();
                Fishing = false;
                Cooldown.Value = Cooldown.Maximum;
            }
        }
    }
}