Game Starting time

Hello folks, new user here. My group has decided to try using Roll20 to play D&D so we can play a bit more frequently than in the past (we've played 3 times this year, last time being in July or August...). Everything is pretty much ready, and we've agreed to play on Tuesday nights, starting at 19:00 (7:00 PM). However, I'm not quite sure when to set the game starting time to here, or what it actually means. Is this when the players have to enter before, or does it indicate when the players can start joining the game? Sorry if my question is a bit confusing or hard to understand... I hope someone understands what I'm asking and that they can help me out here, so my group can have a good first Roll20 D&D session :)

The game starting time is really just for notification purposes. Anyone who has joined the game (appears in the roster of players on the splash screen) can join the game whenever they want to. There is no lockout where players can only join at certain times, however players cannot move to other pages on their own so the GM can keep everyone from seeing what is coming up, but players can still log in to edit character sheets and work on macros, or to read up on any journal entries you've shared with them.