An archive of repair files. Shared as “ARTEL 50A9000 Шасси (Main Board) 40-MT31SS-MAC2H.rar” — a .rar file, 6.40 MB.
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 @led_software. 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.
7-ZipWinRARThe Unarchiver (macOS)