The overshoot for CH4 is already well known from literature and is caused by the inhibiting effect of CO on the reaction rate, while the first overshoot for C2 and C3+ are attributed to the same effect. At the beginning of the build-up phase, the catalyst surface is covered with hydrogen, which is then slowly displaced by adsorbing CO, therefore inhibiting the reaction rate after passing through an optimal ratio between H:CO on the surface. The inhibiting effect explains the initial overshoot and fast decrease, whereas we attribute the second maximum for C2 and C3+ as well as the subsequent slow decrease to a different effect.