You've probably got it right. If you start with a vial or pack of 100 billion cells, and add that to 1 liter of water and 80g of DME with no stir plate you will grow about 80 billion cells resulting in a total of 180 billion. Not all of the sugar will ferment, but on the other hand, oxygen will allow more cells to grow. Experiments I have done with still starteres show that 1 billion cells per gram of extract added is reasonable.