Transfigured gems getting chance.

Hello dear GGG devs
I have a question about transfigured gems getting chance. What the odds to get quality changer after lab runs? And if players get the quality changer , the chances to get exact gems alt quality is higher/100% , or its just like really random gems that we can get? This is really important to know, because its
decisive part of to league start with alt quality gems as main skill or not. Nobody wants to fail league start , so please , understand and give us some information.