Bags of milk

So I live in the best country in North America, Canada. And as such, we drink milk out of bags.
So we buy these bags of bags (yes you heard right) and they come in 3's.
However, the bag advertises 4L of milk.

That means we get 1 and 1/3 L of milk every bag, which is strange. That would mean that you get 1.333333(etc) liters of milk. But, how does a machine mathematically put that much milk in a bag? I dunno. I thought long and hard about this, and then stopped because I realized it was dumb.