Everything is done correctly, but there are a few things left to do: now you just need to use 7z to pack these megabyte files into a 7z archive, and you'll get an archive with the desired 356KB. After that, archive the resulting archive (without compression) into a zip archive (this is only necessary because the forum does not support files with the .7z extension – this is according to the instructions... in principle, you can simply change the archive's extension from .7z to .zip) and you can upload it.

P.S. IMHO, the instructions were probably written in the distant days of dial-up, and today a two-megabyte archive is probably not a problem.
P.P.S. Don't forget to add the extension to the unpacked files? ))