("Mouse Y") is slower than ("Mouse X")

I’ve been trying to see where I went wrong, I’m following the fps guide by quill18 but I can’t see where I went wrong, it seems to not be multiplying (“Mouse Y”), or at least as far as I can tell, (“Mouse X”) goes much faster than (“Mouse Y”)

using UnityEngine;
using System.Collections;

public class FirstPersonController : MonoBehaviour {

	public float movementSpeed = 2.0f;
	public float mouseSensitivity = 5.0f;

	float verticalRotation = 0;
	public float upDownRange = 60.0f;

	// Use this for initialization
	void Start () {
	
	}
	
	// Update is called once per frame
	void Update () {
		//Rotation

	    float rotLeftRight = Input.GetAxis("Mouse X") * mouseSensitivity;
		transform.Rotate(0, rotLeftRight, 0);


		verticalRotation -= Input.GetAxis("Mouse Y") * mouseSensitivity;
		verticalRotation = Mathf.Clamp(verticalRotation, -upDownRange, upDownRange);
		Camera.main.transform.localRotation = Quaternion.Euler(verticalRotation, 0, 0);


		//Movement
		float forwardSpeed = Input.GetAxis("Vertical") * movementSpeed;
		float sideSpeed = Input.GetAxis("Horizontal") * movementSpeed;

		Vector3 speed = new Vector3( sideSpeed, 0, forwardSpeed );

		speed = transform.rotation * speed;

		CharacterController cc = GetComponent<CharacterController>();

		cc.SimpleMove( speed );
	}
}

verticalRotation -= Input.GetAxis(“Mouse Y”) * mouseSensitivity;

the ‘-’ in the ‘-=’ is the problem. I think.