This is a compound measure of a spell’s affect constrained by E.I.R. Casting Theory. High throughput is attributed to greater effectiveness of a spell.
Analogy
Think of nuclear physicists attempting to garner a greater yield within a nuclear reaction. There is so much energy you want to be able to extract from nuclear material, but with good refined and design, you can extract more energy. Same goes with magic. Any spell’s effectiveness can increase or decrease based on throughput.