Normal?

I went in for an ultrasound yesterday, I was supposed to be 6w5-6d and I measured 6w1d but baby had a good heartbeat of 119. No one seemed worried but now I’m wondering if it’s normal! Please share your experience.

*Edit* I should say that I confirmed ovulation with opks so by my ovulation date I should’ve been 6w6d. Just wondering if sometimes babes just start out a little small