\begin{table}%t1
%\begin{center}
\par
\caption{Number of structures of all sizes for the different magnetic thresholds.} \label{tabnb2}
\begin{tabular}{ccc}
\hline \hline
Magnetic threshold & Number & $<Number>$ per image\\ \hline
25 G & 6967532 & 970 \\
40 G & 4291752 & 597\\ \hline
\end{tabular}
%\end{center}
\par
\end{table}