despite the documentation that states it must be a positive value,
the actual implmentation honors a negative number (as opposed to
treating it as a zero, or an absolute).

Change-Id: Ie38369ecdf5353b73572dd3533c2efe41adda290
Reviewed-on: https://gerrit.libreoffice.org/59401
Tested-by: Jenkins
Reviewed-by: Justin Luth <justin_luth@sil.org>