Well, um, TECHNICALLY a 128Mb card has 128Mb of space, not 131.072Mb. It DOES however have 131,072Kb of space, since a Megabyte is technically 1024 Kilobytes, just like a Kilobyte is 1024 bytes.
And that very same 131,072Kb is not 131,072,000 bytes, it is 134,217,728 total BYTES