Chance of pregnancy

So this <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Eve</a> app is telling me that there is a 15% of me being pregnant. However I took a pregnancy test when this app told me there was a 7% chance that I was pregnant and it came up negative. What should I do? And what does this mean? I'm confused.