They don't look like much after just 3 days from popping. The first "leaves" that you see are actually colyedons and don't continue to grow as a true leaf. The next leaves will be single prong and at day 3-4 are quite small usually. The first "true leaves" are 3 prong and you should see those clearly at the end of the 1st week, generally. At that point they will take off. Depending on growing conditions, they can start quite slowly and end up monsters. I find that when I start a seedling too soon under an mh or hps light they grow very slowly for a while, until accustomed to the brighter light. I like 10days minimum under daylight floros.