rabbitmq - heroku celery exceeding connection limit -

i using django/celery on heroku cloudamqp add-on. in settings file if set broker_pool_limit value other none exceed cloudamqp connection limit of 6. i'm wondering why have more connections specify in broker_pool_limit , how can set broker_pool_limit value greater none without exceeding connection limit. in case it's useful, worker process type specified in procfile

worker python manage.py celery worker -b --loglevel=info