XwordField @11,
The message from the extra letters should point you in the direction(s) of the framework.
If you take the single letters in the second element of the framework as illustrating the first, then look across every row, including those that don't have a letter in the second element, to reveal those cells that are in the right place. That will reveal the seven cells, which if you google with 15-30-7 should give you the right one.
As always, hard to describe without being explicit...hope this helps.