What is the probability of finding 4 equal bytes? Is it $2^{-32}$ or $2^{-24}$ as one byte is assumed to take a given value and the remaining 3 bytes should have the same value?
There are $2^8$ one-byte (technically, one-octet) patterns. That implies there are $2^8$ four-octet strings where all four octets are identical out of $2^{32}$ possible patterns. $\frac{2^8}{2^{32}}=2^{-24}$