(Using <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Eve</a> period app)

I'm mega confused. This was my favorite app when i was pregnant, and so I downloaded <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Eve</a> for periods afterwards. However, I used to use a birth control that prevents periods (literally since I was 15!) And so I have no idea how long my cycles usually are. Since I only just got my firat post partum period, I entered the start day. I just keep adding another day everyday I'm still bleeding. My big question is that in the beginning you're asked for how long your cycle is... I'm not sure so I marked the avg 28 days. Will I have to figure it out myself over the course of the next few months and just change it in the app, or will the app pick up on the difference and adjust accordingly?