App says I'm 4 weeks....

Rebecca
<a href="https://play.google.com/store/apps/details?id=com.glow.android.nurture">Nurture</a> tells me I'm 4 weeks and 2 days. Really I could only be 2 weeks from the day we conceived. Is this correct? Does the app just count from the last period? Just wanted to know to keep updated (correctly) on what the baby is up to :)