In my journeys I have come to learn that if ur going from seed, wait for them to show there sex be4 countdown. If u veg for a long period of time then obviously they will show there sex during veg and can start countdown as soon as u flip to 12/12.
If u veg for a short period in which they have not shown there sex, and are flipped to 12/12, u have to wait for them to show there sex during the flowering period.
From clone:
She has already shown her sex and can be transplanted to 12/12 as soon as roots are visible. Let the countdown begin! Hope this helps.