What does this mean?

Today was my first ultrasound appointment and I went. I didn’t think we would see much of anything. I was more concerned about if I was having twins. Anyways my last period was July 20th 2019 and I tested positive on August 12th 2019. Glow days I ovulated on August 3 and another app says I ovulated August 2nd but when I had my ultrasound and you clearly can see a baby I was surprised 😲 and baby is measuring 8 weeks 1 day. Anyone else have this happen to them? This is my 4th pregnancy 🤰🏽 and I don’t remember my baby measuring bigger than when I ovulated. Heart rate was 160. Can anyone give me any insight on this and if this has happened to you or know of anyone it has happened to. Thank you 😊