Due date ?

Glow gives me a due date while doctors give me a diffrent one. I honestly don't remeber when was my last period so I just took a quick guess , meanwhile I always tracked everything down on glow. So in my perspective is glow more accurate with my due date ? Doctors say 21 & glow states the 25 , Is there any chance the baby could be maybe 4 days late after the 25 ?