Xiaomi Mi 4C service package, a RAR archive of about 1018 KB. The name states the model only, with no board revision or description of the files inside, so unpack it and confirm what it contains. Packages of this size for a phone normally hold schematic PDFs, which let a repairer follow power rails, test charging and display circuits, and pinpoint components on a shorted line. Before relying on the drawings, check that the PCB markings match. Do not confuse it with the Mi 4 or Mi 4S sets.
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 @cyberlanelectonik. 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.