What does this mean?

Brittany • 20....married since 7.16.14. TTC #1.
Ok everyone, I need your help. I'm new to this bbt charting thing. (I just started yesterday) and tester day June 25 my bbt was 97.8 and today June 26 my bbt is 95.8. What does a drop in temperature mean? And is this a normal drop? According to Glow, I ovulated on June 17.