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Ok, we are talking about apples and oranges.
Of course if you transfer a file, then the file will arrive at the same size. A file of 1024 bytes consists of 8192 bits and thus you transfer 8192 bits of user data.
But the line needs some more capacity because of protocol overhead. If your ISP says your internet line is 16 MBit per second, then you get only ca. 1.6 MByte per second file download speed and not 2 MByte as your formula expects.
In the same manner if you see a file transferred with 32 KByte per second, then you can expect your line to have 320 KBit per second and not 256 KBit per second as with your formula.
The transmission size increases on the lower protocol levels. At the highest level (where you looked at) the file size certainly remains the same. But to transfer one byte user data the line has to carry ca. 10 bits. The additional 2 bits are filtered out by the protocol stack at the receiving side. They are used for error recognition, packet ordering and so on.
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