When you add Monitors like MS SQL or any Service Server type, the host of the database will automatically get discovered as an "Unknown monitor". This monitor will consume a license. You can choose to edit and update the correct details of the host or delete the monitor. You can later add the servers as Windows monitors if required.
To opt out of automatically creating unknown monitors in the future:
From AppManager UI, navigate to Settings Tab --> Global settings and uncheck the following keys:
1. Add Host also when you add a new service.
2. Add Host as a Monitor when you associate a service running in it to the monitor group.