"Pick one," Even Milena commanded Arthur to pick one, curious what Lucifer had planned.
No one realized that Lucifer actually had two plans in his head, and he simply wanted to leave the selection to luck at this moment.
He had placed one choice on the middle finger selection while the other was on the index finger selection.
"Fine. I select the index finger," Arthur let out, making a choice. He remained alert in case there was a surprise attack, but no attack came.
"That one, huh. I was also tilting more towards that one. So be it," Lucifer muttered, lowering his hand.
According to Lucifer, if Arthur had chosen the middle finger, that would have implied that he needed to show a middle finger to all the concerns and go towards the path of stealing Milena's powers.
As for the Index Finger, it was the choice of selection of him going for the kill and not leaving Milena alive.