The Mixer pictured above, publishes its equalizer characteristics in the manual as:
with 6dB gain and infinite cut on all controls (infinite cut is questionable).
Typical controls have symmetric boost and cut.
Typically in this kind of eq system (having only 3 bands), the Hi and Low bands are implemented with shelving controls, and the mid control is a low Q bandpass filter. The filter skirts typically overlap at the 6dB rolloff points to offer a flat response at mid settings. To meet this goal (flat response) the frequencies listed by the manufacturer may be interpreted as corner frequencies for the Hi and Low bands and center frequency for the Mid band.
You should probably contact the manufacturer if you want exact specifications for these controls, or run a plot with each knob in each of the following (min, center, and max) positions to varify the manufacturer's eq implementation.
I had posted a general link to the typical three band tone control used on amps. The link was removed as the information was a bit off topic.