Chart confused

Almas

Hey... I was using fertility friend app as well as glow both apps at first showed my ovulation on CD14 but on CD 18 when I entered by bbt Fertility friend app changed my ovulation from CD14 to CD15 why is it so... Please tell me when I exactly ovulated... Here are both Fertility Freind and Glow bbt chart... Should I override my Fertility Friend chart?