: The term "rar" refers to the command-line version of WinRAR. In these environments, numerical strings are often used to define specific search parameters, hex strings, or file attributes within an archive.

If you can clarify the or software you are working with, I can provide more targeted information about how these codes should be applied. winrar/rar.txt at master · Aerovin/winrar - GitHub

: In European Union environmental regulations, numerical codes like 2017/999 refer to specific Commission Regulations, such as those governing high-temperature coal tar pitch used in specialized industrial applications.