Which fields maintain the link between Jira and Aha! integration

[Aair Murta]

I'm looking at integrating Aha! roadmaps with Jira and see you can sync: Jira release with Aha! version Jira Story with Aha! Feature Jira Story with Aha! Requirement

What I am struggling with is finding a document or article on which fields are used to maintain the relatinship between the identities e.g. If a Jira release goes to sync with Aha! version which field is used to match the records so the corresponding Aha! version is updated?

Thanks!