Files from third-party PKG sites can contain errors or, rarely, malicious content. Ensure you have antivirus software active during extraction.
The extraction will produce a .pkg file, which is a game dump designed to be installed on a jailbroken PS4 console . BatmanArkhamKnightUSAPKG-pkgps4dotcom.part09.rar
This file is one part of a larger download (usually part 01, 02, etc.) used to distribute large PlayStation 4 games ("PKGs"). Source: pkgps4dotcom (a third-party PS4 game hosting site). How to Use Files from third-party PKG sites can contain errors