Just for the record, most of the milk in HK is not sold by the litre, it is sold by the quart, which is 946ml. This is a quarter of a gallon.
Only the Australian Pura, Greenfields, and a few other brands are sold by the litre. The local Kowloon Dairy, Nestle, trappist, etc are sold by the quart.
You may not realise this because a quart and a litre are very similar shape/size. But they are not the same. HK has no standards and no consumer protection in areas like this. In Australia, it would be illegal to sell milk by the quart because it is misleading and there are standard sizes you must conform to. I am guessing in the US its probably illegal to sell by the litre.