Confused on Ovulation Kit

Elise

Hello, I am brand new to the TTC journey. Well more like if it happens it happens. I got the ovulation kit because I wanted to know if the apps are right because my periods are CLOCKWORK and the app has always been correct on when my period is (except once). I took it and it seemed as if it was dark enough to be positive for ovulation and then then next day it was lighter. Does that mean I ovulated yesterday or does that mean it’s today I am ovulating?