Which day to mark LH SURGE???

I am trying to figure when my LH surge started so I can mark it on glow. No LH on 3/2 with BBT of 97.9 and The top one is from 3/3 with BBT OF 97.8 and the bottom one is from 3/4 with BBT of 97.4. so I think  I'm ovulating today just don't know if I should mark it as the 3/3 or 3/4...any help would be great ☺️ thanks ladies....