Relationship between MT listing and Subscription

Manisha has explained to us that if a subscription expires, then the Mosets Tree directory listing attached to that subscription will get unpublished automatically.

I looked at the db table (jos_payplans_subscription), and tried to understand how the Payplan subscription and the Mosets Tree link_id are connected, and cannot find any relationship between them. I only find a relationship between the user_id and the subscription_id only (which means that the same user can have multiple subscriptions with multiple Mosets Tree listings) see screenshot http://prntscr.com/hupspl . Can you please explain to us how the exact link_id of the Mosets Tree is connected in the db with the subscription_id? We're trying to understand this to customize a feature we want to make.

Thanks,
Mohammad