Glow app saying 5 weeks??

Kelsey

I am so confused is anyone’s <a href="https://play.google.com/store/apps/details?id=com.glow.android">glow app</a> accurate about how far along they are? when I type in my last period on due date calendar it says I would be 4 week and 1 day and my due date would be September 10th but glow says I am 5 weeks and my due date is September 5th I am so confused which one is right???