Due date confusion

OK, so based on my last period, I am due June 30. Then I went in and had my appointment and my doctor said July 2. But I changed the calculation on this app based on what the baby measured at my appointment (Monday she said measuring 10.3), and my due date is July 1! Which one would you use? I know they are within days of each other, but when people ask me I don't know what to say!