Are ultrasounds not very reliable for predicting ovulation?

I had an ultrasound today and they've dated me 6w4d.
That puts me at conceiving on the Friday and I had an attempt that day. I also had an attempt the Monday beforehand.
Just wondering if its unlikely I got pregnant on the Friday attempt if I ovulated that same day?
Hope that makes sense!

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Yes, these types of ultrasounds are a bit unreliable. We just can't know. You could have Oed a day later or even two, or you could have conceived from the Monday attempt and Oed on Wednesday or something like that.