Scrog Q - when to flip

It's common to read flip when 80% of the screen in full etc, but I struggle to understand this.

My whole screen is covered with growth, ie can't see the pots they sit in if you look down at them from above so the foliage is filling the screen well. I have quite a few tops, enough that I can't count them and provide a figure (though can uploads pic tomorrow when I have access to a pc to upload the pics.

Is there a set number of bud sites I should look to get within my space 1.2x1.2m or distance or space between each bud site I should aim for?

the goal of the scrog is to create a field rather then a christmas tree style of growth people generally flip at "80%" because when you flip to flower the plant undergoes stretch and would fill out the rest of the screen and your field would be complete giving equal penetration to each bud side. If you fill out the screen to much and the stretch hits you will most likely end up with a uneven canopy and nodes sitting on top of one another which negates the whole productivity of scrog.

Thanks of the response, though it's not really answered my question.

I understand the advantages of a scrog, I have my screen in place and am nearing the stage of flipping the lights to 12/12. Again 80% tells me little, my screen is full of foliage.... 80% of the holes in my screen filled? Or what else could 80% mean? So what's 100% filled, 1 bud site per hole? I have a lot o holes in my screen. I'm just confused with the seemingly vague yet commonly used terminology.

I don't want to flower with too few bud sites and ruin the whole idea behind a scrog- in my case to maximise yield by maximising on the surface area in my tent.

There's not a bud site in each square in my screen, i imagine it would be too cramped if there was, so I just want to know how much space others using this method leave between bud sites so I can apply this to my grow to work out when to flower and maximise my yield.

it is truly all in the positioning that the plant arrives at the screen and you begin to stretch out among the net, generally yes you want one bud site per hole but depending on how many plants you used, height, and length all determine how well you are going to be able to get "1 bud site per hole" once again yes that is ideal one bud site per hole and nothing growing out of the screen for instance say you have a few empty holes in your screen but you are running out of the length on the sides then you will sacrifice over growing your screen to fill in the remainder which would probably be worse of an outcome then just flowering it in the first place. Simply put try your best to fill up your screen if you don't fill every hole its not the end of the world if you run out of places to pull and put then you can learn from the experience and try to get a more complete screen on your next grow.

P.S pictures are worth a 1000 words