From a more grounded perspective, "Download 581K zip" is likely a from early web development:
Those who claim to have successfully unzipped it describe a chaotic mess of text files containing "impossible" data—logs of chat conversations that haven't happened yet, or lists of names of people who would later go missing.
Eventually, the repetition of this specific file size across hundreds of unrelated, sketchy sites turned it into a "glitch in the matrix" meme within communities like 4chan and Reddit's r/UnresolvedMysteries. Summary of the "Full Story"