Hello everyone) On September 14th, I checked and went out one stripe, …

Hello everyone) On September 14th, I checked and went out one stripe, but I felt like I was pregnant. According to the numbers 16-17, it should have come these days. Delay. Then on the 21st, exactly a week later, I checked again with two stripes, on the second day of blood hCG test, and confirmed my pregnancy. They said about 4 weeks!!! Can you please tell me why there was one stripe on September 14th? It shows a positive result on the 3rd or 4th day of conception.