Here is the manual: »
www.start.ca/files/smart ··· 505n.pdfI'm guessing the QoS is designed mainly to prioritize an IPTV stream that runs on a different VLAN. There's often no documentation for features like this and they usually don't work as you'd expect them to, but feel free to experiment.
It boggles my mind why someone hasn't put out a consumer device that just prioritizes small-sized udp packets, which would cover VoIP and gaming without the user having to configure anything..