Many my dubts have been solved by this documentation:
https://kb.juniper.net/InfoCenter/index?page=content&id=KB24728&cat=NS_5400&actp=LIST
Nevertheless I don't still understand what are the ingress and egress interfaces. The number 110 is not an ID associated to an interfaces. in the "show sys" output there isn't the 110 number.
And what about my last question? Is there a way to understand if the flows in the "get session" output work or not?