How Smallrye-reactive-messaging-jms Consumer choose between listenner/receive

[CarlosPanarello]

I'm testing a new application using smallrye-reactive-messaging-jms with IBM-MQ.
It works like a charm, but I'm a little confused about how this library chooses to consume messages using receive or listener.
Looking at JmsSource, on line 116, this request method calls a listener or receives and it is a override from Flow/Subscription, how n is set with value inside this reactive pipeline, but how this count n works, where is changed, is by request from mutiny pipeline ?

Thanks in advance.