How to make sense of error message?

I have an error and i got this error message :

ArgumentOutOfRangeException: Argument is out of range.
Parameter name: index
System.Collections.Generic.List`1[UnityEngine.Vector3].get_Item (Int32 index) (at /Users/builduser/buildslave/mono-runtime-and-classlibs/build/mcs/class/corlib/System.Collections.Generic/List.cs:633)
PolyDrawExample.Update () (at Assets/PolyDrawExample.cs:69)

The problem for me is that i cannot pin point the error, i know the rough area where it is as i had just created a method and when i saved it and flicked back to the editor and ran it i saw the error. However this error could be in several places which i believe are all fine. I think the 693 in the error message is a clue but i only have 231 lines of code so i am confused. (I cannot click on it and it will take me to the error, presumably because it is linked to a generic list which involves another namespace). So what does it mean? If you are willing to have a look at my code i will edit it in.

In short what does the 633 in the error message mean? And How can i get to it?

Thanks, any help is much appreciated.

Double-click on the error message in your console and it will take you to the exact line. The message also lists the line and script: PolyDrawExample.cs, line 69. The 633 refers to the line of code in the script of the Generic List, which is of course not directly available to you since it is included in Systems.Collections.Generic.

The error message means that you try to access an index in the list that is beyond the List’s length.