How are SetCPU frequencies formulated?

Are the frequencies suggested by SetCPU for each device based on a certain algorithm or was it worked out device specifically or are they just arbitrarily formed upon extensive testing? I have an old HTC Wildfire which has a maximum frequency at 768MHz The steps of frequencies show by SetCPU itself is 176,264,352,518,576,614,633,652,672,691,710,729,748,768 all in MHz. I eventually created a setcpu.txt file which I put in the root of the SD-Card. The thing is when I had a frequency of 800MHz SetCPU still read it but the max frequency it could obviously touch was 768MHz. I repeat, my question is how are the frequencies listed by SetCPU formulated?