Your experience with two sacs but one heart beat!

I am 6 weeks and 5 days. I had my first ultra sound appointment and they found two sacs. The heart rate in one was 110 and the other didn’t have one. My doctor said that i am early and the heart beat may pick up or it was a develop of soothing but it didn’t finish. Please tell me your experience!! I am very thankful for the healthy heart beat, but i can help but to wonder about the other! Thank you all for commenting!