\begin{tabular}{@{}c
    S[table-format=2.0]
    S[table-format=2.1]@{}}
\toprule
                 &\multicolumn{2}{c}{\textbf{Amount (\%) for a starter}}\\
                          \cmidrule(rl){2-3}
\textbf{°C / °F} & \textbf{Recently fed} & \textbf{Starving}\\ \midrule
        30 / 86  &  5 &  2.5 \\ 
        25 / 77  & 10 &  5   \\ 
        20 / 68  & 15 & 10   \\ \bottomrule
\end{tabular}