Basically, it’s counting interactions provoked by cards with ratios made of ressources of your opponent divided by your ressources. Study credit swings. Etc.
Something like Tour guide, for exemple, cost a card and a click, will cost a click and 5c to the runner if this works.
=> you will gain from 1 to 4 clicks on the runner if this works. It’s a good tempo card.
Neural EMP’s damage is -1clic for your opponent, and this cost a card, a clic and 2c (aka 3-4 clic trading for 1)
Coreset have cards giving medium to high ratios, then first expensions are low and this ratio is increasing through expensions.