With "Play on this many days ahead" schedule, you can run your webinar X many days ahead.
Let's say you want to always run a webinar that will always run at 1 pm but 1 day ahead. So if the visitor goes to the registration page today, they will see that the webinar is available tomorrow at 1 pm. Then you can set the time option like this.
If you want to add multiple options, then you can just hit "Add a scheduling option"