When did I ovulate?

My OPK was positive starting in the AM on CD14 with EWCM, OPK was still positive through CD15, negative on CD16. I am new to OPK so I’m not sure, the <a href="https://play.google.com/store/apps/details?id=com.glow.android">glow app</a> put my ovulation date as CD15 🤔