Progesterone levels

Monday 3/7 I went for my 2nd US to see if I was responding to the letrozole (I did not respond at 5mg, but did respond at 7.5mg) got my peak ovulation on 3/8 at about 8pm. And I got my progesterone level drawn on 3/15. They said my levels confirm ovulation and that my level is at a 13, but they prefer it to be at a 15. I’m currently 8/9 dpi (I don’t know if I should count 3/8 or 3/9 as my ovulation date) but with all that being said anyone have a BFP after having a 13 for their post ovulation bloodwork? They put me on progesterone suppositories (200mg twice a day) just looking for some advice. This is the first time we have been this far.