parallel hint not spawning right number of parallel processes

hi !

I am using the /*+ PARALLEL(14) */  hint in querries and what i noticed is that sometimes it does create 16 parallel processes and sometimes it doesnt and sometimes it creates only 4. 

what could be causing this behaviour ?    below are my parallel settings .

SQL> show parameter parallelNAME TYPE VALUE------------------------------------ ----------- ------------------------------fast_start_parallel_rollback string LOWparallel_adaptive_multi_user boolean TRUEparallel_automatic_tuning boolean FALSEparallel_degree_limit string CPUparallel_degree_policy string MANUALparallel_execution_message_size integer 16384parallel_force_local boolean FALSEparallel_instance_group stringparallel_io_cap_enabled boolean FALSEparallel_max_servers integer 24parallel_min_percent integer 0parallel_min_servers integer 4parallel_min_time_threshold string AUTOparallel_server boolean TRUEparallel_server_instances integer 2parallel_servers_target integer 8parallel_threads_per_cpu integer 2recovery_parallelism integer 0SQL>nothing is also in the  queue