I think you're confusing Hertz with bytes. Data is measured in binary figures, so a KB is 1024 bytes, a MB is 1024 KB, a GB is 1024 MB, etc.
Frequency has nothing to do with binary data, and Hz is used to measure anything that happens X number of times per second. So its just a decimal number. 1000 Hz = 1 KHz.
Edit: Typo.