Calender question

🙈🙉🙊 • Mom to 2 amazing little boys.
I just got my first positive opk since my miscarriage. I've logged the past two weeks as no surge on the calender. I logged that I have my surge today and it changed and says yesterday was my most fertile day. Shouldn't today be my most fertile? Maybe I'm confused. I'm not ttc again yet so it's not a big deal. Just trying to understand it.