So I am pregnant woohoo super happy!

I have a 23 day cycle my last period was the 28/12/18 (DD/MM/YY)

So because my flow app wouldn’t let me change my “status” to begin with I decided to look online with first response to figure out how far along I am and it says 4 + 1

But few days later my <a href="https://play.google.com/store/apps/details?id=com.glow.android">glow app</a> let me change my status to pregnant so I did and I typed in my LMP, how many days in my cycle and it’s saying 4 + 6

But both say I am due the 29/09/19 (DD/MM/YY)

But when I am counting 40 weeks from LMP then my due date is 04/10/19 (DD/MM/YY)

So I am baffled any body able to help me out? Thank you 😊