I’m not actually sure how much is sent. You need about a tablespoon’s worth in order to culture 8 oz of milk in a timely fashion, according to some things I’ve read. I think companies usually send them dehydrated, then you reconstitute them in milk for a few days before they start working (might happen in the fridge? I would hope the company selling them would tell you). Since they’re little colonies of bacteria and yeast (that’s why they eat the sugar), they gradually reproduce as they consume sugars. After a while, you’ll have lots more than you started with.