It reduces it from ~64^password_length to ~3^password_length, and that assumes that the password is a random jumble of letters. If it's a long phrase, like "I k

It reduces it from ~64^password_length to ~3^password_length, and that assumes that the password is a random jumble of letters. If it's a long phrase, like "I know the entropy of English words isn't terribly high, but a lot of them make a better password than what people typically choose", the effect is even stronger.