Which day(s) were you looking at? It looks like Lamplight Lounge "closes" about an hour before the park does on most evenings in September for when park hours are posted. So on nights when DCA closes at 8:00 pm, Lamplight Lounge "closes" at 7:00 pm. I saw a couple of reservations for a little past 6:00 pm on those nights. On nights when DCA is open until 10:00 pm, I saw a few reservations for times around 8:00 pm available. For the nights when there are Halloween Parties in DCA, the park closes at 6:00 pm, so Lamplight doesn't technically have a dinner service listed at this point. My guess is that they'll continue to seat walk-ups until about 5:00 pm (or there about), but they might not take reservations.