Assets/Scripts/PlayerController.cs(32,49): error CS0126: An object of a type convertible to `float' is required for the return statement

Can someone please tell me what this means?

 using UnityEngine;
 using System.Collections;
 
 [RequireComponent(typeof(PlayerPhysics))]
 public class PlayerController : MonoBehaviour {
 
 
     public float speed = 8;
     public float acceleration = 12;
 
     private float currentSpeed;
     private float targetSpeed;
     private Vector2 amountToMove;
 
     private PlayerPhysics playerphysics;
 
     // Use this for initialization
     void Start () { 
         playerPhysics = GetComponent<PlayerPhysics>();
 
     
     }
     
     // Update is called once per frame
     void Update () {
         targetSpeed = Input.GetAxisRaw ("Horizontal") * speed;
         currentSpeed = IncrementTowards (currentSpeed, targetSpeed, acceleration);
     }
 
     private float IncrementTowards(float n, float target, float speed) {
         if (n == target) {
                         return; // this is the line it says
                 } else {
                         float dir = Mathf.Sign (target - n);
                         n += Time.deltaTime * dir;
                         return (dir == Mathf.Sign (target - n)) ? n : target;
                 }
         }
 }