RAR archive of 152 KB named QT6A-MB-C, which looks like a motherboard code for the QT6A project, revision C, though no brand or file type is stated. Unpack it to determine whether it is a boardview, schematic or firmware. If it is a boardview, it opens in programs such as OpenBoardView or FlexBV for locating parts and test points. Verify the code and revision printed on your PCB match QT6A and C before trusting component positions or flashing any image.
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 @schematicslaptop. 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)