Question to parents of twins or pregnancy experts, am I going to have twins??

My wife is currently 4 weeks 4 days pregnant. We just went for her first ultrasound to make sure everything was looking alright, and it is. Ultrasound only showed one gestational sac. But everyone who hears where here HCG is either thinks we are wrong about how far along we are or that we’re going to have twins. Even the ultrasound tech admitted she was kinda expecting to see twins. My wives last bloodwork was 3643. I know they can range wildly person to person and I will be happy with any healthy babies but I just want to have as much time to mentally prepare myself as I can. So, what does everyone think my chances are based on that information? Should I calm down a little or should I start buying two of everything now lol