Need help determining/understanding which week im on!


So my approximate due date is Feb 15 2023

When i input my last period it says im 4weeks and 6 days into my pregnancy

However on the weekly development dates:

Week 1 & 2 may 12- may 25

Week 3 may 26- june 1

Week 4 june 2- june 8

Week 5 june 9- to june 15 (TODAY IS JUNE 14TH)

Week 6 june 16- june 22

Why is there a difference in weeks between the <a href="">due date calculator</a> and the weekly development dates from the SAME website?

How does 4 weeks and 6 days the same date that falls into the second to last day of my 5th week?