These files usually contain textures, scripts, or patches. For example, a "No glowing eyes" mod or a specific weapon overhaul might be packaged this way for easy extraction into a game’s "Data" folder.
The Royal Australian Regiment Association maintains extensive bibliographies and digitized libraries that often use such numbering for their sub-collections. 2. Software & Gaming: Mod Archives 1-6.rar
1. Military History: 6th Battalion, Royal Australian Regiment (6 RAR) These files usually contain textures, scripts, or patches