This is where you'll drown in numbers if you don't have a frame of reference (or, as I like to say, a good relationship with the plant.)
Just one variable expands to so many permutations of other variables. And that one variable you thought you had controlled changes when you grow the next plant
It's life we're dealing with, after all. Biology loves to laugh in the face of our reasoning... so we often have to trust whatever effective processes we can identify and reproduce (or, as I like to say, have a good human/plant communication.)
Just like Aqua's guide to watering.
It's not prudent to try to figure out media saturation and evaporation rates until you know what a plant looks like when it's wilting or overwatered.