8K Upscale with H.265 created 2 files

I was upscaling a video for youtube to help with compression issues. More of a see if it works experiment I exported a 4k H.264  .mp4 file to a H.265 8K in .mp4 after it was complete I was left with 2 files one .m4v and one .mp4 Is this expected or did I miss a setting in the export? Also which file should I upload?