It means nothing special, you are simply viewing raw binary in some manner of bad editor and @ simply means value 0x40, or perhaps 0x0040. Perhaps the editor is using a symbol format (some UTF?) where most of these raw hex values don’t make sense, but it was able to represent 0x40 or 0x0040 as @.
I’m guessing this binary goo is from the PE Format for Windows executables.
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