\begingroup
\small
\setlength{\tabcolsep}{4pt}
\begin{tabular}{rcrrr}
\toprule
$J$ & Branch & $m_{\rm fit}^2$ & $c_{\rm fit}$ & Max. rel. error\\
\midrule
128 & $u$ & 0.00009977 & 0.99951711 & $4.178\times10^{-4}$\\
128 & $v$ & 1.00160745 & 1.00086504 & $8.703\times10^{-4}$\\
256 & $u$ & 0.00004223 & 0.99977748 & $2.020\times10^{-4}$\\
256 & $v$ & 1.00035280 & 1.00011615 & $1.782\times10^{-4}$\\
512 & $u$ & 0.00001288 & 0.99993124 & $6.311\times10^{-5}$\\
512 & $v$ & 1.00008799 & 1.00001936 & $4.499\times10^{-5}$\\
\bottomrule
\end{tabular}
\endgroup