"Not as many as you should be," Sirius said briskly and — sensing that for whatever reason James needed more contact — unfolded his arm from under his head and casually began flicking his fingers against James's ankle. He turned James's two points over as his best mate tackled the goose/pillow/whatever, not appearing to notice the loud honking noises it made — Sirius had a gift for tuning out anything he couldn't be bothered with.
"The beacon is a good point," he said, a touch slowly, as he considered the ramifications of that. "I've been assuming the conductor was some kind of Being with his own sentience, and that he's in the employ of someone or another... but it could be that he's actually part of the bus. If the bus is a Beast, then it could be its nature to draw in magical — and magically-adjacent — beings, and there's no greater point to any of this."
Sirius looked back up at the ceiling, and carefully looped the words 'Alt: Beacon drawing us in' in big enough handwriting that it flowed across both the 'Flagging it down' and 'Fare' columns. "I don't know which reasons are important yet," Sirius admitted, something he was greatly reluctant to say to anyone other than James, or perhaps Lily. "I don't want to risk us overlooking something because neither of us thinks it's relevant enough to bother with."
Sirius does them both the service of not saying, out loud, why he has developed this very particular kind of caution.