NSX UI reports an alarm "The number of objects defined in the system for Active Directory Domains (Identity Firewall) has reached 2 which is above the minimum capacity threshold of 70.0%"
VMware NSX
The alarm triggers when the configuration maximums has reached its limit.
For example :-
NSX Manager with Medium Sized supports 2 Active Directory domains and NSX Manager deployed with Large size supports upto 8 Active Directory Domains.