In a single server, there can be multiple instances of Oracle/MSSQL database. Each instance is counted for licensing in Applications Manager.
Example 1:
In the above image, you can see that there are 3 instances of MS SQL DBs in a single server, namely MSSQLSERVER, SQL008R2, SQLEXP2016.
These 3 databases are considered as 3 different monitors even though it is in a single host.
Example 2:
Similarly, each of the above mentioned Oracle database instances will be considered as individual monitors for licencing.