If you’ve used the Reset Helpdesk feature to delete your test tickets in Admin > Reset Helpdesk.

The counts of tickets in the agent interface Navigation Panel might still include the old tickets, you can remove them by enabling Ticket Archiving. Go to Admin > Ticket Structure > Statuses > Archived, then toggle the setting to Enable Archived Status:

On the same menu, then click Reset search index to reset the counts to zero:

You can disable archiving after this if you would prefer to not use the archive status. Note that archiving is typically only needed for helpdesks with a large number of tickets (over 1 million).