How Close to Curtain can Tickets be Bought at a Box Office?

I bought a ticket through TDF to see the matinee of Sunset Blvd today, and one of my friends has also decided that they want to go. We're totally fine not being seated together (we don't expect the theater to be able to accommodate that at this point) but she wanted to wait until I picked up my tickets to see if she could buy one that is as close to my seat as possible.

Would the box office sell tickets within like an hour or a half hour of curtain? I feel like they probably would/do but I've never tried to buy tickets without at least a few hours before a show so I don't know if there's like a cutoff at a certain time.