Currently, there are seven options to choose from when configuring your Daily Digest:
- Overdue tasks
- Tasks that start today
- Tasks that start tomorrow
- Tasks that start in the upcoming 7 days
- Tasks that are due today
- Tasks that are due tomorrow
- Tasks that are due in the upcoming 7 days

I think it is missing an option to include tasks, that have already been started in the past, but still are not finished (kinda like 'overdue', that is).