All of the .7z files are part of the same archive. If you extracted one file you extracted them all, because if you didn't have all the appropriate files your extractor would have complained. If you really want to find out if you needed it, you can move that file elsewhere on your hard drive and try extracting again to see if your extractor complains or not.

In any event, now that you have successfully extracted the files from the archive it doesn't matter anymore whether or not you know you needed the file (though I'm sure you did.)

BTW, Good job Harmy. I downloaded the SD version and it looks great.