Magicite Knight's Materia Eruption Question

[Viladin]

So I'm having trouble understanding how Materia Eruption really works. If they sense multiple magicite auras, do they pick which one they want to affect? Or is it random? Or is it reliant on how many rounds they use to sense the auras?

Reliant on how many rounds.

1st round: Random materia.
2nd round: Can pick the highest level materia.
3rd round: Can pick and choose any materia.