The 'Call details' stored on the PostgreSQL DB has retentionship period for 6years as per business needs to keep their Archive calls for 6years.
So “Retain Call details for (months)” is the information stored in the Postgres database for both archived and call buffer calls. So since storing calls for 6years on the Archived, there is need to also have the Call details retained for 6years.
In that case, the best option will be for the business to expand the disk space to accommodate the call details retained for 6years so calls on the Archived can be played back otherwise the ACR will not know about those calls and will hinder playback.