The total number of monitors, will include the monitors that we add by default. These default monitors will not be taken into account while calculating the number of monitors for Licensing.
If you do not want a particular monitor to be included for licensing count, you can unmanage it (data collection doesn't happen). More information on Manage / UnManage option from Help Document. While unmanaging a monitor, monitor count will not decrement but will remain the same in Category view. The list of Managed and Unmanaged monitors can be viewed from Bulk Config View. If you have a license of 250 monitors and in Bulk config page, you have less than 250 monitors under Managed category then you can add new monitors. Unmanaged monitors will not be taken in for licensing count.
Yes, Annual Subscription fee includes phone suppport.