Well, for what I remember Henry already out of the hospital when the bet game came.
All four of them is in some room maybe on chase mansion, Isaac started the question wondering how josh seems to be acting strange, (I can't remember all details but Henry kinda hurt here and his side comment like how did he even like Isaac was funny.) things escalates and from josh changing job and them reasoning the cause of josh behavior, Henry started the bet after placing cash on the table. They bet on josh might be changing job, had some illness or seeing someone. Although most of them disagree with Josh seeing someone, Seth said he even saw someone confess to josh although josh rejected the confession. (While all this was happening Henry was taking notes on his phone and bet that josh was also gambling I think) Then since they can't really accept Seth answer they ask him to guess who might it be Henry said he'll double Seth winning if he guess it correctly. So Seth answer C, cause he believes it's the most unlikely person josh to be having relationship with (since I believe he's pitying Henry at that moment) and so the chapter end on them being loud.
Please, pardon my English, I'm not that fluent on it haha
Also I believe there's a round two for this after josh decided to confess to his team about him dating...

Ah, the whole betting on josh thing is way longer and funnier on the novel. It was one of my fav scene from the side chars but I guess they can only put this much on the manhwa, still it's good