Why does my method "Vector2 SpawnPosition()" cause erratic behavior?

So I have an infinite spawner based on distance that spawns an object every time the previous object is 10 units away, but this only works for the X spacing and does not allow me to alter the Y spacing, therefore I have to alter it afterwards. It will all make sense once you read the code.

What happens is that when I use SpawnedObject.transform.position = transform.position;, the spacing is all fine and dandy, but when I use SpawnedObject.transform.position = SpawnPosition(-10, 10);, the position.x starts to get crazy and erratic. Meaning it will spawn like 2 units away, or sometimes 6 and so on.

Why is it doing this and how can I fix it?

Here is a picture of the problem http://imgur.com/YIXSK8X The logs are supposed to be separated by 1 square which is 10 units.

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 
 // This script creates a list of type objects and allows you to use the objects in that list.
 
 public class ObjectPool : MonoBehaviour
 {
 
     //when using this for other GameObjects, just change the class name to _w/e.
     public static ObjectPool instance;
     public GameObject _object;
     public int poolAmount = 20;
     public bool willGrow = true;
     public float newSpeed;
 
     public List<GameObject> pooledObjects;
 
     public float distance;
     public int ObjectSpacing;
     private GameObject SpawnedObject;
 
     private float randomXPosition;
     private float randomYPosition;
 
     void Awake()
     {
         instance = this;
     }
 
     // Use this for initialization
     void Start()
     {
         pooledObjects = new List<GameObject>(); //create object pool
         for (int i = 0; i < poolAmount; i++)
         {
             var obj = (GameObject)Instantiate(_object);
             obj.SetActive(false);
             pooledObjects.Add(obj);
         }
        
         SpawnNextObject(); //Spawn first object
     }
 
     void Update()
     {
         distance = Vector2.SqrMagnitude(SpawnedObject.transform.position - transform.position); //calculate distance between this object and objectpool start position
         
         if (distance > (ObjectSpacing*ObjectSpacing))
         {
             SpawnNextObject();
         }
     }
 
     public GameObject GetPooledObject()
     {
         for (int i = 0; i < pooledObjects.Count; i++)
         {
             if (!pooledObjects[i].activeInHierarchy)
             {
                 return pooledObjects[i];
             }
         }
 
         if (willGrow)
         {
             GameObject obj = (GameObject)Instantiate(_object);
             pooledObjects.Add(obj);
             return obj;
         }
 
         return null;
     }
 
     private void SpawnNextObject()
     {
         SpawnedObject = GetPooledObject();
         //SpawnedObject.transform.position = transform.position;
         SpawnedObject.transform.position = SpawnPosition(-10, 10);
         SpawnedObject.SetActive(true);
     }
 
     Vector2 SpawnPosition(float minY, float maxY)
     {
         if (minY != maxY)
         {
             randomYPosition = Random.Range(minY, maxY);
         }
         else
         {
             randomYPosition = minY;
         }
 
         var obstaclePos = new Vector2(transform.position.x, randomYPosition);
 
         return obstaclePos;
     }
 }