Ultrasound measuring later but know when I ovulated

Went and got a private ultrasound at 6weeks4days. There was a heart beat which is good but the ultrasound tech said they measured 5weeks6days which isn't possible because I tracked my ovulation and got a pretty early positive test. Anyone have this happen and everything be ok? I think the ultrasound tech might have also measured wrong. She seemed nervous and unsure of herself. And it's not a medical facility technically but that kinda worried me, especially since I know I can't be 5weeks 6days it's not possible.