RAR archive of 470 KB whose name gives only the token A400, with no brand, board number or revision to identify the hardware. The size suggests a small set of documents or a firmware image rather than a large schematic set, but the contents cannot be confirmed from the name alone. Extract it with WinRAR or 7-Zip and inspect what is inside before use. If it holds a schematic, boardview or BIOS dump, compare the board number printed on the PCB with the files, and back up any original flash chip before writing anything to it..
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @one5technology. Enginerys does not host this file.
How to open a .rar file
Compressed archive — the usual wrapper for a schematic + boardview pair or a BIOS + EC set.