Thanks for playing the game :)
Yeah, we didn't have time to explain the mechanics in the game.
Basically when you're on the level-up/evolve screen, the items on the left side is what is currently on your ship. The items on the right are newly generated modifiers.
With sliders, you pick which side you want to have more % to inherit, but the balance across all sliders has to be equal.
But honestly, it's just an unfinished system.