(Following paragraphs copied from bug 116236 verbatim)
As mentioned in
http://developer.gnome.org/doc/tutorials/gnome-i18n/developer.html#plurals,
the common way of handling plurals is broken for many locales. A way to
solve this is by using ngettext instead, as mentioned in that document.

A simple code example of code using ngettext:

  g_printf (ngettext ("Found %d file.", "Found %d files.", nbr_of_files),
nbr_of_files);

This is the relevant message.

#: backends/xml-cache.c:343
#, c-format
msgid ""
"%u items remain in the cache after cleaning already-synced items older than %"
"u seconds"

This one is a bit tricky, because it contains two uses of %u, so it would
have to be split into two parts, and those ngettext-ed separately, for
instance:

"%u seconds"
"%u items remain in the cache after cleaning already-synced items older
than %s"