A project network consists of the following activities
\[\begin{array}{|c|c|c|} \hline \textbf{Activity} & \textbf{Immediate Predecessors} & \textbf{Duration (days)} \\ \hline \text{A} & \text{--} & 3 \\ \hline \text{B} & \text{--} & 4 \\ \hline \text{C} & \text{A, B} & 5 \\ \hline \text{D} & \text{B} & 6 \\ \hline \text{E} & \text{D} & 7 \\ \hline \text{F} & \text{C, E} & 8 \\ \hline \text{G} & \text{D} & 9 \\ \hline \text{H} & \text{F, G} & X \\ \hline \end{array}\]
If the project completion time is 30 days, then the value of \( X \), in days, is \(\underline{\hspace{2cm}}\) (in integer).
