For a great portion of the outliers, the 'decision maker' selects multiple dead-end molecules, which approaches the expected costs of multiple hundreds. By learning from trial-and-error results, the policy model reduces the expected costs of most target molecules, with median expected costs being stabilised below 10 in the last five iterations and finalised at 5.2 at the last iteration. Along the 20 iterations, although the portion of outliers also reduces, there are still outliers that reach costs over 200 in the last five iterations. These are large protein molecules which usually have molar weights over 500 and are believed to be hard to synthesize, which include C16-KDO2-lipid A, UDP-4-amino-4-deoxy-L-arabinose, etc. The situation of target molecule ferricytochrome c has not been improved over the 20 iterations, which stabilises at the expected costs of 704 in the biological reaction pathway in Figure .