By default the value is set to 4. To adjust this follow these instructions:
Go to the Cisco Unified Communications Manager web administration page, and choose System> Service Parameters.
Note: Choose Service > Service parameters for Cisco CallManager 4.x.
Choose the publisher server from the Server drop-down list.
Choose Cisco call manager service from the Service drop-down list.
Select the Maximum MeetMe Conference Unicast parameter under the Clusterwide Parameters (Service ) section. You can increase or decrease the meet-me sessions for the conference.
Complete these steps in order to increase the number of participants or sessions for a meet-me conference on Cisco Unified Communications Manager.