I mix ~500 ml of water with somewhere between 3/4 c and 1 c Huel making the volume of one shake ~600 ml having approximately 450 calories.
There is another thread that tried to get clarification of the 5:1 ratio thing, but the staff reply still didn’t make sense to me.
I suppose the post-mixed volume of my shake does come out to about 5:1 but that is not especially helpful when needing to measure the dry ingredient (displaced volume in the mixture will not equal the measured volume).