gender prediction and conception date

this is my first scan and the tech says is likely a girl because of the three lines.(nena means girl in Spanish). the thing is that i have a problem with the dates. from what i was told if you are 16 weeks pregnant then your baby is 14 weeks approximately from the date of conception. well, my problem is that i was charting and i ovulated 24 days after my period, almost a whole month. does that puts my baby at 13 weeks from the date of conception and thus predicting the gender would be inaccurate? the tech had problems with the measurements of the baby, they told me it was probably too small, based on my last menstrual period, but that's my point, i think it is because i ovulated so late that they are getting smaller measurements and not because the baby is not growing.he/she was conceived on july 1st and my last menstrual period was june 8th. i would greatly appreciate if anyone could help me with the gender prediction and if i am correct about the weeks issue based on my late ovulation. i mean, most women ovulate 14 from their last menstrual period and i ovulated 24 days later that's nearly 2 weeks more. thanks . i'm including the ultrasound photo and my fertility chart.
ps: if you can tell me the location of my placenta that would be great! i found a research paper discusing the location of the placenta and the gender prediction. it's called ramzi's method and is about 97% accurate at determining gender. i just don't know if my placenta is on the right or on the left. thanks