Three lines on scan mean girl?

I'm not finding out the gender, but it doesn't stop me speculating hehe. I've heard two horizontal lines mean a boy and three vertical lines mean a girl, am I getting that theory right? And would that mean this pic is of my little girl or little boy? (Scan pic from 12 weeks). Would love to see any comparisons also from those who know or think they know what they're having 😄