For me, maximum motoring is when N2 does not accelerate anymore because of the 30psi duct pressure spinning the starter motor has spun the starter motor and consequently, the N2 to the maximum speed that it can spin both; at this point, you don't see an increase in N2 rpm because of the pneumatic start effort reaching its maximum capability. This is when you are sure that letting fuel into the engine won't result in a hot start (or a wet start).