From the moment you send an invitation you will receive an update of your event every 3 days:
The number of registrations.
Statistics of the last sent mail (open / click / bounces).
Statistics of the website visits.
The number of cancellations, if a reason has been given by the invitee, it will also be shown here.
You can change the frequency in your profile settings. Go to your dashboard. Click on "Profile". Under frequency of event updates, you can choose how often you want to receive the emails.