The First warning is received by default when you reach 80% of the specified quota (you can adjust this if you right-click the parent node, go to properties, synchronization, general, Notifications)
When you reach 100% of licensed units, this error is received:
Warning:<Quotas Manager> (5123) Licensed Free/Busy objects quota. The quota was exceeded.
or
Warning:<Quotas Manager> (5123) Licensed Active Directory objects quota. The quota was exceeded.
Please examine your Aelita License Key File (filename.ASC) Please make note of the AD Objects=xxxxx portion of your license file.
If the total Number of Synchronized objects exceeds the number specified in your Aelita License Key file, please contact your sales representative to obtain additional licenses for these added objects..