Well, for one thing, your syntax is wrong. It should be:
SELECT FROM(SORTIN) TO(SORTOUT)-
ON(1,33,CH) ON(44,9,CH) FIRST DISCARD(SORTXSUM)
Note that you need a separate ON field for each key, and positions 44 to 52 have a length of 9, not 8.
If that doesn't give you what you want, then give more details of what you're trying to do including an example of the records in your input file and what you expect for output and the RECFM and LRECL of the input file.