A day of content is usually six or seven sessions, depending on which day you get placed in. Days can also be extended with evening (Birds of a Feather) content.
If your event is selected, you will have complete control over the sessions which are scheduled in that event, although they will need to line up with the session times of the larger event, so that attendees can jump between tracks if desired. (Sessions may be 45 minutes, or 20 minutes, to fit into those slots.)
When you have submitted your proposal, please also join the planners list by sending a blank email to firstname.lastname@example.org