When can I get pregnant in my cycle?

👩🏻

Okay I know this is a stupid question. I am a grown woman, and I have one child already. But I got pregnant right away with my first, and never had to TTC for long. I know there is a day you ovulate, and supposedly you get pregnant around then. That’s the only time you can get pregnant. But why does the app say you have a 3% chance of getting pregnant the day after your tracked period ends? Also, about a week after my period ended in June the app said I had 13% chance on one day. So how if you can’t get pregnant until those days that you ovulate?