But we're told people never learn more then 1 element, the lines are your basic effective vs ineffective (or neutral) pokemonesque combat style.
That's the blue and red lines.
From the next drawing and the fact Haneul is an ice witch, I guess people have 1 or more "starting" element, and then can invest in this elements for cheap, or a bit more in the ones with affinity, and even more for the others.
Let's say someone has fire magic. They can spend 1 point to gain 1 level in fire, 2 for one level in wind and water, 3 in lightning and earth, 4 in dark or light. If they have 10 points, they can spend all on fire to be a strong level 10, or be a weak level 2 in fire, wind and water (2*1+2*2+2*2), or a weak level 1 in fire and 3 in earth (1+3*3).
So most people would focus on one element and be strong in it, instead of being weak in multiple ones, unless they're a genius/monster/anomaly like the witch.
At least that's how I interpret it, based on decades of playing RPGs.