Exactly what I said... it depends on your headphones.
The web page is right with the frequecies... 8,000 kHz would be 8,000,000 Hz, or 8 MHz.
If they were to be displayed in kHz they would have to be 8 kHz - 22 Khz.
And the frequency range on your headphones is 10 Hz-39,800 Hz, not kHz... Huge difference.