I'm guessing because you're not really making "15 million of something". The process is more like making one or two (or ten) batches, which is then sub-divided

I'm guessing because you're not really making "15 million of something". The process is more like making one or two (or ten) batches, which is then sub-divided into 15 million doses. It'd be like the difference between burning dinner 7 nights in a row, versus making a single mistake during Meal Prep Sunday and ruining a weeks worth of dinners all at once. The latter is much more understandable.