The -h option is supposed to sort numerically when the numbers are in "human readable" format (i.e., 42k instead of 42137), as in the matching -h option for ls (and other commands). And the "+4 -5 -h" will sort on the 5'th column. It works great if you aren't using -h (sort +4 -5 -n, with a regular "ls -l" command). Also, works if the number is in the first column (as in: du -h |sort -h).