are you sure about the ATF-WS?
Can you verify it from the manual?
Prius has a CVT gearbox so Toyota CVTF(same oil used in new vitz, axio and new shape altis 1.8 A/T) should be used
ATF-WS(recommended for automatic corolla 2008-current(1.6L alits)) is for newer cars with Planetary Gearsets