This has been Air Force staple for many of us monitors for years.
The first 6 letters/numbers are usually the unit the message if for,followed by the actual message.It is usually repeated twice ("I Say again")
It is then decoded by the unit and is usually just a practise message.
I myself really enjoy listening to these,,I have no iea what the messages are but just hearing them makes listening to the shortwave fun
That frequency (8992) is one of a few that constitutes the 'HF-GCS' or, High Frequency Global Communication System. You should also try 4724, 6712, 6739, & 11175 as EAM's are broadcast simultaneously. It's a great method to see what kind of propagation is happening at that time.