Updated b/c no AF yet and prev fertility dates changed?

An
Question for Glow Support Crew ...
​can't remember what date my fertility window was originally forecast by glow, but it used to be around the ❤️'s on my chart cause that's when my hubby was home so we had a great time BD'ing!  Still no AF so I updated my period dates and it's moved the fertility window to what you can see now which is about a week later.
​I'm confused!  Why has this happened?