GRIZZLER.
Did they 2-step it? DE-ICE the aircraft to obtain a clean wing then ANTI-ICE to prevent reform and give sufficient holdover time to get airborne? In falling snow, it is normal to 2-step the aircraft as DE-ICE only doesn't provide much holdover.
Maybe they only need 320 ltrs of DE-ICE fluid to clean the surfaces (not that contaminated), then ANTI-ICED afterwards. Just a thought