[Setting] MaxQueueThreads [Description] 
Specifies the number of threads used by the Report Server Windows service to process subscriptions and notifications simultaneously on the report server. Valid values range from 0 to maximum integer. The default is 0. If you choose 0, the report server determines the maximum number of threads. If you specify an integer, the value you specify sets the upper limit on threads that can be created at one time. For more information about how the Report Server Windows service manages memory for running processes, see Configuring Available Memory for Reporting Services.