When is my accurate due date?

Ti

Hay ladies sorry for the weird question I’m just confused with the due dates the <a href="https://play.google.com/store/apps/details?id=com.glow.android.nurture">nurture</a> app and my doctor have given, so my last period was on the 2nd of November and lasted till the 8th (7days) and my cycles are normally 31days (average) so I’m trying to figure out the due date, glow is saying 11th of August but if I count weeks from day 1 it’s the 8th of August, just wondering which way I should count it?