Generic numeric filenames (like 30.rar or 1.rar) were often used by automated scripts to distribute trojans, info-stealers, or ransomware .
If already downloaded, use a service like VirusTotal to check the file's hash before attempting to extract it. 30.rar - AnonFiles
If you tell me this file was associated with (e.g., a specific game mod, a tool, or a leaked database), I can help you identify its intended "feature" or provide a safer alternative. How to Open RAR Files on Windows, Mac, and Mobile - Avast Generic numeric filenames (like 30