a) previous RAR version failed to unpack folder records in archives created by RAR 1.50. RAR 7.01 Update: New Features & Fixes - Scribd

Specifically, in , the archive format included a feature where folders were stored as specialized "folder records". This feature is considered "informative" because modern versions of RAR often treat these legacy records as metadata or informational cues rather than standard files to be extracted normally. Technical Details of RAR 1.50 Features

The phrase refers to a technical behavior in older versions of the RAR (WinRAR) compression utility.

: Recent updates (such as RAR 7.01) have had to specifically address bugs where the software failed to properly unpack these older "KG 15" era folder records. RAR 7.01 Update: New Features & Fixes - Scribd

a) previous RAR version failed to unpack folder records in archives created by RAR 1.50.