Confused! Baby sizing!

Natalie • I’m 21 and trying for baby number 1😽🎀

So I have finally been told that I am pregnant! I went for a dating scan and the lady said I was 7+6 weeks but the baby is only 7.7mm. Everywhere I have looked online says at 8 weeks it should be around 1.6cm??

Am I thinking too much into this, I’m worried my baby is already too small?