Moving GameObject with Mouse problem

my camera is at 0,0,0 as you can see in the script below, my mouseInput.x / ScreenWidth * 16 statement, i used the print method to see my mouse and see how big my screen play space is and it is 16 across with my mouse , my problem is when i hit play , my paddle starts of at the end of the right side(position 8) and only goes to the middle of the screen , when i move my mouse to the middle of the screen its at position 0 when i move the camera over half way to the right , it works perfectly (so it starts at 0), is there a reason why my paddle starts at the end of the right side instead of the middle. am i doing this wrong ? When i move the paddle with the arrow keys i dont have this problem. i already have a way to find out the left and right side of the camera and i have them in a variable called xmin and xmax and using it to restrict the paddle in between those points, i do not know what am i doing wrong. i am completely lost been at it for days. Also when i remove the Screen.Width / 16 from float MousePos = Input.mousePosition.x/ Screen.width * 16; my paddle is placed out of screen to 480 on x posistion , so that did not work either. thank you i think i need to have it so it starts at what ever position its at right?

 using UnityEngine;
 using System.Collections;
 
 public class Paddle : MonoBehaviour {
 
     public float Speed = 1f; 
 
 
 
     float xmin;
     float xmax;
     float padding = 1f;
     // Update is called once per frame
     
     void Start(){
 
         // get Right and left side of the camera
         float distance = transform.position.z - Camera.main.transform.position.z;
         Vector3 leftmost = Camera.main.ViewportToWorldPoint(new Vector3 (0, 0, distance));
         Vector3 rightmost = Camera.main.ViewportToWorldPoint(new Vector3(1,0,distance));
          xmin = leftmost.x + padding;
         xmax = rightmost.x - padding;
     }
     
     
     
     void Update () {
     
         print(Input.mousePosition.x/ Screen.width * 16);
         Movement ();
         
     }
     
 
     
     
     
     void Movement(){
 
         //get mouse inout
 
         float MousePos = Input.mousePosition.x/ Screen.width * 16;
     //    //constrain paddle to the right and left edge of camera.
         float newX = Mathf.Clamp (MousePos, xmin, xmax);
 
 
         this.transform.position = new Vector3 (newX
                                         , transform.position.y, transform.position.z);
     }
     
     
     
 
     
 }