Which day did you count as CD1?

Do you count the first day of bleeding as cycle day 1 or the day your hcg levels were negative? I bled for 10 days but my levels didn’t reach negative until my 10th day. I started opks the day after the bleeding stopped. Had all negatives (blank smiley faces) and i ran out before i got a smiley face positive. The day after i ran out and for the next 3 days i had good ewcm. The day i got my ewcm was 14/15 days after my hcg levels hit negative. Curious what everyone else thinks!?