NIPT testing

They only took one vile of blood for the NIPT test, is that normal? And also what will it indicate when I get the results back next week? A lot of people told me I’d find out the gender but they said they got 3-4 tubes of blood drawn which confuses me since the nurse only needed 1 from me. My anxiety has been making me question this all day 🤦🏼‍♀️