[Koha] Question about the staffClientBaseURL and OPACBaseURL system preferences

Dear all, I'm wondering whehther these two system preferences are supposed to work onr not. I'm trying to install Koha on a system where I don't have root permission. The only thing I have is a personal web directory where I am allowed to put an .htaccess file. It is worth mentionning that these files can't contain Alias directives and the like. So, I set e.g. staffClientBaseURL to somehost.somedomain.net/koha/intranet/ And then I thought that the URLs generated by Koha would all start with this prefix, but this did not happen. Do I misunderstand something ? Thanks in advance for any help, Sébastien.