The ticket number should be set as the real seats are available, the actual number os tickets you can issue.

This number does NOT limit the invites sent Pending can be infinite.
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This number does not limit allocations to Ticket owners. Pending can be infinite.

Consumption of the real number will auto-close the RSVP.

The number can be increased or decreased at any time.

This number set this way will enable accurate utilization analysis in our dashboards

Hope this helps you set the Event Tickets number.