Where can I see how many tickets have been scanned?

To see how many tickets have been scanned, log in to your Billetto account and find your event in "My events" at the top-left panel. Click 'Manage' next to the relevant event. 

You will find the number of scanned tickets under "Check-in status" in "Attendees" section in the left-hand side panel

You will see a graph displaying the totals and timings of your scanned tickets.