CCN8909 The subscript %1$s is out of range. The only valid subscript is 0.

Explanation
The user attempted to index an array with a value that is not within the bounds of the array. 

In the message text:

"%1$s" is the index into the array 

User response
Change the index so it falls within the bounds of the array or increase the size of the array.
This message is usually generated when the user tries to index the array with the size of the array
and forgets to subtract one. 