I am 1 week late in my pregnancy , is it ok?

Pari

I am 9 weeks 4 days according to my last period day and according to my app. But on ultrasound I am 8 weeks 5 days. I am sure the date when I was ovulated, as I took ovulation test. Why I am 1 week late? Is it ok to be late? I don’t want to think anything negative on this pregnancy but it keeps remind me last two miscarriages. Hope this time everything is going well.