Shannon entropy is a measure of how much new information each symbol in a communication channel gives us. In the case of a PRNG, if we know the seed then each s

Shannon entropy is a measure of how much new information each symbol in a communication channel gives us. In the case of a PRNG, if we know the seed then each symbol tells us nothing because we can generate the exact sequence from the seed, hence the Shannon entropy of each symbol is zero (provided you know the PRNG and the seed! - if you don't then you can determine them from a sequence, but that's another topic!).