Complex sentence: It is "entropy per symbol" when the logarithm base is equal to the number n (not N) of distinct i symbols, which is a normalized entropy per symbol that ranges from 0 to 1.
Split into simpler sentences: It is "entropy per symbol" when the logarithm base is equal to the number n (not N) of distinct i symbols. This is a normalized entropy per symbol that ranges from 0 to 1.