Over/Underclocking?

It'll be documented

System clock = 8Mhz * N / ( M * P )

so

8*192/(63*8) = 3Mhz

But it's in the reference manual under 6.2. Reset and clock control (RCC) for STM32F401xB/C and STM32F401xD/E then Clocks.

The diagram at the start is the interesting bit.