"Implantation bleeding" is an Internet myth. An embryo is smaller than the dot on the i in this sentence. When it implants in the uterine lining, it usually produces no sign. In the rare case, there might be a little wisp of blood in the vaginal secretions. But not days of bleeding that is as heavy as a period.
Also, the actual measurements of your actual baby in your 7th week ultrasound indicate it was a period. If you had gotten pregnant July 17, you would have been in your late 10th or early 11th week on September 19. The scan didn't show an 11th week baby; it showed a 7th week baby.
Sometimes babies come early. It doesn't reach back in time and change the date they were conceived.