When you think about it, Suteguma's bait-first answer of 8, from other party's point of view, was basically just guessing, right? The first round of Dotty hasn't even happened yet, and he already instructed Hyougo to put that into the terminal. At that moment Suteguma couldn't possibly gathered enough information to correctly deduce Baku's number, so in all fairness, it's not strange that Baku already noticed the scheme and already coming up with a counter-scheme.