Bullet Damage Player's Healthbar,Bullet Damage Other Player's Health

Hi,I setted the bullet script that when i shot a player his healthbar take 10% damage,but when i shoot a player his healthbar go to 10%.
Bullet Script:

    void OnCollisionEnter(Collision collision)
    {
      GameObject hit=collision.gameObject;
      Health health=hit.GetComponent<Health>();

      if (health != null)
      {
        health.TakeDamage(10);
      }

    Destroy(gameObject);
  } 

Health Script:

    public const int maxHealth = 100;
    public int currentHealth = maxHealth;
    public RectTransform healthbar;

    public void TakeDamage(int amount)
    {
        currentHealth = amount;
        if (currentHealth <= 0)
        {
            currentHealth = 0;
            Debug.Log("Dead");
        }

      healthbar.sizeDelta = new Vector2(currentHealth * 2, healthbar.sizeDelta.y);
    }
}

Sorry for my bad English,
Wrasty

@grdomenico
Health Script:

 public const int maxHealth = 100;
 public int currentHealth = maxHealth;
 public RectTransform healthbar;
 public void TakeDamage(int amount)
 {
     currentHealth -= amount;
     if (currentHealth <= 0)
     {
         currentHealth = 0;
         Debug.Log("Dead");
     }
   healthbar.sizeDelta = new Vector2(currentHealth * 2, healthbar.sizeDelta.y);
 }

}

This is the fixed version, you forgot to take away the amount instead you were setting your health to it!!!

Thanks very much!!