The signal optimization step of the OptiEIS experiments can take (at a minimum) as long as 2 cycles of the minimum frequency entered during setup. During this step the current measurement range of the potentiostat is selected based on the amplitude of the signal. The "Max Current" box of the setup screen determines the initial current measurement range used during optimization. The optimization can take much longer, by multiple attempts at signal optimization, if the Max Current is too low, as it has to switch to the next range up and reattempt. The best method is to make an educated guess of the maximum current value with some knowledge of the impedance of the sample.
If you notice excessive noise in your OptiEIS data it may indicate that the Max Current value is too large. The potentiostat cannot switch down to lower current measurement ranges during the optimization step in order to prevent overloading the hardware for extended periods of time. Again, the best method is have an educated guess of the max current value. If an educated guess is not possible, it is better to err on the side of a lower Max Current value, as it still allows the potentiostat to switch up to higher current measurement ranges if the signal amplitude is too high for the initial range.