There are two "shelving" controls on Peavey amps. A high and a low. The "low shelving" simply controls all the lower frequencies and the "high shelving" controls all the higher frequencies. These controls will give you a starting point to control your frequencies (basically , your over all tone.)
The slider EQ controls are for specific frequencies. If one string or just a few notes seem stronger or weaker than the rest , you can use the sliders to adjust them. Your overall tone comes more from the shelving controls.
The corner frequency is (I believe) supposed to be the high frequency of what the low shelving controls. I never paid much attention to frequencies on the shelving controls because due to harmonics , they have an effect on all the frequencies. I just use my ears to find what sounds good to me.
On my Peavey amps with similar controls I usually set both shelving controls around 1 or 2 o'clock (a slight boost for both controls.) When I'm using my P Bass , I set the sliders for a slight mid boost (frown face.) When I'm using my Ibanez , I usually set the sliders for a slight mid cut
(smiley face.)
Play around with all the controls to find the sound you like. The shelving controls will have the most effect on your tone and the EQ sliders will let you "tweek" those tones. Enjoy.