He is giving insight into the Ye Ji an mi ng connection.
There is a document that talks about transferring something from Romania to Jordan in coordination w the Chicoms. The clear implication also is that they are using subs to transport it/them to Jordan due to the submarine commander mentioned in their correspondence. I'm having a brain fart to his name but i normally know it. He is a well know whistleblower against Bdn.
My guess is this is they were transferring children to the sex slave markets attended by many Muslim leaders in Jordan.
The news isn't mentioning this document yet but i believe they will.
Outside of any deductive reasoning we could deduct from the letter what it confirms is that at least Hunter was involved w CCP agents in smuggling something from Romania to Jordan by the means of a nuclear sub captain.