Getting weird error message!?!?!?

So im trying to generate a random 10 digit number everytime the left mouse button is click but when i click it the numbers are replaced with this “system.collection.generic.list 1[system int32]” can someone help me or guide me to the right place to fix this

using UnityEngine;
using System.Collections;
using UnityEngine.UI;
using System.Collections.Generic;

public class GenerateNum : MonoBehaviour {
	public Text numGen;
	private int maxNumbers = 20;
	private List<int> uniqueNumbers;
	private List<int> finishedList;

	void Start () 
	{
		uniqueNumbers = new List<int>();
		finishedList = new List<int>();
		

	}
	// Update is called once per frame
	void Update () 
	{
		if (Input.GetMouseButtonDown (0)) 
		{
			Generate ();
		}
	}

	public void Generate ()
	{

		for(int i = 0; i < maxNumbers; i++)
		{
			uniqueNumbers.Add (i);
		}
		for(int i = 0; i< maxNumbers; i ++)
		{
			numGen.text = "" + finishedList.ToString ();
			int ranNum = uniqueNumbers[Random.Range(0,uniqueNumbers.Count)];
			finishedList.Add(ranNum);
			uniqueNumbers.Remove(ranNum);
		}

}
}

@KamiSama00 The trouble is in:

finishedList.ToString ();

This code turns the list object to a string, rather than turning the content of the list to a string.
You will have to write a function to do that for you.