Because the file itself is a .7z archive, you need a compatible decompression tool to "look into" it:
When you open a "7z Extra" archive, you will generally find the following components: santa_extra.7z
You can use 7-Zip on any computer, including a computer in a commercial organization. You don't need to register or pay for 7-Zip. How To Install 7Z / Zip Files Because the file itself is a