Glow vs. Ovia

Angel
So I am using both the <a href="https://play.google.com/store/apps/details?id=com.glow.android">Glow app</a> and the Ovia app. I put the same info in both. Glow tells me 3% chance of pregnancy for today and Ovia says that today is a 10 (on a scale of 1-10) for fertility. Why would there be such a discrepancy between the 2 apps? 🤔