InstallMate sets this variable if one or more installed files are also registered for post-boot deletion. This can happen if the installer runs after another program (including possibly the uninstaller of the previous version) tried to delete a file but found it in use. InstallMate always tries to unregister any such files, but this may fail if the current installer is running with insufficient privileges. You can use this variable to warn the user and perhaps schedule a reboot followed by a repair.
You can refer to this variable as <TsuPendingFileDelete>. In conditional expressions you can omit the brackets and use tests like TsuPendingFileDelete to test for pending file removals. Set automatically by the installer.