First ultrasound with an unexpected surprise

Hey everyone! So I need some help. I had my first ultrasound today. I am six weeks and one day. The technician took pictures of the baby, and then said “uh oh there’s another one!” Of course I almost fell off the table. However, she said baby b is way smaller than baby a, but there is a heart beat. She only gave me the pictures for baby a and said right now we’ll just say it’s one baby until she can talk to the doctor. My question is, has anyone who’s had twins and an early sonogram had this happen? I’m a little nervous because I want to have two healthy babies. Any advice or words of encouragement would help! Thanks!