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If the unnecessary cruft doesn't push the file over a 4 KiB boundary, then it's a non-issue. Hard drives store files in chunks of 4 KiB, known as a
disk sector. If my zip archive has a size of 3996 bytes, and then I increase its size by 100 bytes, then it still takes up exactly one disk sector. Those 100 bytes weren't going to be used.
On the flip side, if the archive has a size of 4096 bytes, and my unnecessary cruft increases its size by one byte, I just doubled its size on disk.
Yet both of these facts overlook an even more important fact. A 4 KiB increase in size on an 80 GiB drive is, well, how can I demonstrate this...
4096: 4 KiB (the smallest possible increase in disk size)
85899345920: 80 GiB (a small hard drive by 2014 standards)