Slider changes value by yourself

I have two camera so i have to monitor. One camera keeps canvas. The other one watch game. When i click 'A' and 'D', the slider triggered and changing values. I don't write 'onKeyDown' or like this. How can it possible ?

Here is my codes:

 public class ChangePlanetSize : MonoBehaviour {
     Slider planetSlider;
     public GameObject [] Planets;
     public Vector3 [] PlanetsDef;
     // Use this for initialization
     void Awake(){
         Planets = GameObject.FindGameObjectsWithTag ("Planets");
         PlanetsDef = new Vector3[Planets.Length];
         for (int arr = 0; arr < Planets.Length; arr++) {
             PlanetsDef [arr] = Planets [arr].transform.localScale;
         }
     }
     void Start () {
         
 
         planetSlider = GetComponent<Slider> ();
         planetSlider.onValueChanged.AddListener (delegate {ChangeVal ();});
     }
     void ChangeVal(){
         for (int arr = 0; arr < Planets.Length; arr++) {
             if(planetSlider.value == 1 )
                 Planets [arr].transform.localScale = PlanetsDef [arr] * planetSlider.value ;
             else if (!Planets [arr].gameObject.name.Equals ("Sun"))
                 Planets [arr].transform.localScale = PlanetsDef [arr] * planetSlider.value * 200;
             else
                 Planets [arr].transform.localScale = PlanetsDef [arr] * planetSlider.value;
         }
     }