Tickets.app will begin importing your Tickets after you complete the initial setup process.
You may begin using Tickets.app immediately. The activity window will show the current progress of the import process.
Ticket importing will ultimately import all of your cases. Importing begins with the highest numbered cases first.
The import process is broken into 'blocks', each of which represents a range of Tickets to import.
If you exit Tickets.app before all of your Tickets are imported, it will resume when you restart Tickets.app