Period late. AF pushed back?

Alisha • 35 years old 🐕 Wife + Dog Mama | UI | IVF ❄️ 7 frozen embabes | 6 MC’s

So, I’m currently 4 days late based on when my period was actually supposed to be here (11/7). The app asks if my period started and when I️ say no, it pushes the day by 2 days. Which pushed my ovulation window all different. What is this science? When should I️ take a test?