There's no problem to put a little bit more tempeh starter.
The amount of the tempeh starter needed for 1 kg cooked soybeans (500 grams dried soybeans) is 1 gram tempeh starter. However, it is difficult to make the fixed amount of tempeh starter for each soybeans. So it would be better if you increase the flour, not the tempeh starter. (mix 9 grams of flour to 1 gram of tempeh starter).