Off dates.

Kelsey
I had a mc September 30th and found out 2 weeks ago I'm pregnant. This app says I'm seven weeks based on what I put for my last period which I just put the day I had the mc I never had another period since the mc. I went to my first appointment today and baby looks good and measures five weeks five days does anyone know how I change the date on this app so that it says I'm five weeks not seven?