I took another look at the Solution.app--it isn't broken. I think what happened is the test table is too small and the disk cluster size is screwing up the results ... for their orditems table the index on STR(line_no) is the same size as the index on line_no, where line_no is an integer.
So index size is no mystery--I just work from the # of bytes the index expression requires.
----------
Mark Bucciarelli