4 week ultrasound?

Melody

Hey everyone. So, I had a dating ultrasound done and I found out I’m a lot earlier on than I thought. I thought I was 6 weeks because of my first day of my last period but but the ultrasound she could only see the beginning of something (a dark black spot) and confirm a pee test. Is this normal? Is that what a 4 week ultrasound looks like? I found out later in with my other two boys so I’m just making sure.