Vincent listens patiently, nodding a couple of times--once at the mention of magic, and once when Phalanx confides that they are "a lot", in whatever sense they feel that to be true. Vincent finishes the last bite of his skewer, chewing thoughtfully, before blindly reaching back and dropping it into the bag it had originally come from.

"I don't really understand that kind of stuff very well," he admits, "But I believe you."

Again, Vincent isn't a smart man by most accounts. But he doesn't need to be. He doesn't have the same fixation with understanding every minute detail of every interaction that Robin constantly chases. He can coast along pretty far on very little. He doesn't need to understand how a pile of souls could exist to imagine that it probably gets pretty fucking crowded and busy in there. If Phalanx says they're a lot, Vincent has no reason to doubt them, especially because he's heard them be more honest in casual conversation than most humans with only one soul to work with.