Quoted from Andreas' comment:

Please change the man page to use "K, M, G, T, P" suffixes, even if the
code accepts both. Those are the correct SI suffixes for these units. It
probably doesn't make sense to list units of bytes here at all.

This would also be a lot better as a separate lfs-setquota.8 man page,
since I don't think this command is available to regular users, and it
would allow you to have a proper section describing each of the options
properly instead of only this short blurb.