: This indicates the file is part of a "split archive." Because high-quality remuxes can exceed 50GB or 100GB, they are often broken into smaller RAR segments to make them easier to upload and download. If one part is corrupted, only that segment needs to be re-downloaded rather than the entire massive file. Digital Archaeology and Preservation
: Likely a shorthand identifier for the content and the release group. "B4R3" (often "Bare") could refer to a specific group known for high-bitrate video encodes. x310-b4r3-remux-rem-part13-rar
The use of split RAR files (like Part 13) is a legacy of the early internet. In the era of dial-up and early DSL, downloading a 40GB file in one go was impossible. Today, even with gigabit fiber, the practice persists because it remains the most reliable way to verify data integrity through checksums (SFV files). Conclusion : This indicates the file is part of a "split archive