tar backup script

[Steel City Phantom]

this isn't really bsd specific but i still need help with it.  im writing a
backup script  a clip from that script is this:

find /usr/local/www/data-dist/ -name config.php >
/usr/local/backupScript/include
find /usr/local/www/data-dist/ -name ClientFiles >>
/usr/local/backupScript/include

tar cvf /usr/local/backupScript/files/www-client-files.tar -I
/usr/local/backupScript/include /usr/local/www/data-dist

obviously im creating an include file from a directory.  when the tar runs,
it correctly adds all the files in the include file.  but once that is
finished, for some reason tar then goes back and adds all the files that are
in the /usr/local/www/data-dist directory, even the ones in the include
file.  i was under the impression that the -I command would add ONLY the
files that are listed in the include.  why is it adding those and then after
finishing that, adding all the others?