Change in edd

Kristi • I'm a stay at home mom to a little boy who's 2 years old. I'm currently pregnant with my second who is due 10/17/16.
How can I change my edd in the app? I had my first scan today and baby is measuring 7 weeks 1 day(edd Oct 17) but going from my LMP(which is what the app does) I was 8 weeks(edd Oct 12).