The limit for the ticket inventory is based on the Quantity Remaining value for the Event Level in Luminate CRM, which is calculated based on the Quantity Available minus the Quantity Registered. If the Quantity Registered field is blank when the event level is created or modified, then the system also leaves the Quantity Remaining field blank.  Luminate Online then interprets this as "No Limit". If you put any value (such as 0) in the Quantity Registered field, that calculation can proceed and the Quantity Remaining is updated in both systems.