The pitch C4 has a frequency of 261.63 Hz, so at a sample rate of 8,363 Hz, each single cycle of the waveform has exactly 32 samples. 32 is a power of 2, so C3 will take 64 samples, C5 will take 16, and so on.
When sampling a C, this sample rate avoids unnecessary clicking at the loop point caused by a sudden change in value, or the pitch being slightly off due to the sample being slightly too long or short to compensate.
It's a pretty cunning sample rate, just so long as you're not concerned about compatability with more popular devices with fixed sample rates, such as DAT recorders. When trackers were popular, sampling would have involved digitising an analogue source, so this wouldn't have been an issue. Even a digital source such as a DAT would have very likely been converted to analogue and back to digital again, sampling via a humble unbalanced cable.
Exactly twice this frequency, 16.726 kHz, was also sometimes used. I'm not aware of anything using 33.452 kHz, as the Amiga, which trackers originated on, could only play back samples at up to about 28 kHz or so.
As far as I'm aware, neither sample rate was ever used by musicians using professional samplers, nor anything else outside of trackers. Perhaps they were missing a trick — S950 users, take note!
With the introduction of fixed rate samplers such as the S1000, this arcane knowledge has become obsolete. If you're still using a variable rate sampler, though, it might just be worth trying out, to make your life that little bit easier.