My fertility window moved when changing my period date?

Katie • I am 28 years old. I have been with my husband for 7 1/2 years, married for 2 1/2, and have been trying for babies for almost 2 years.
I have not started my period yet, I'm 7 days late, so I changed what the app said was my estimated day, and then noticed that it changed my fertility window and ovulation day. I'm not sure if it did it bc I have not started yet?