I am trying too decrease the space between the captions in the makebox and the figures I am displaying with the following code;
\begin{figure}%
\centering
\begin{adjustbox}{minipage=\linewidth,scale=0.9}
\hfil\hfil\includegraphics[width=8cm]{mainmatter/1/Chapter_4/heat_maps/hs4_original_heatmap.pdf}\hfil\hfil
\includegraphics[width=8cm]{mainmatter/1/Chapter_4/heat_maps/hs4_heat_predicted.pdf}\newline
\setlength\parindent{0pt}
\null\hfil\hfil\makebox[5cm]{Original incidence matrix \protect\linebreak ${\bf M}$.}
\null\hfil\hfil\makebox[5cm]{Surrogate incidence matrix \protect\linebreak $\hat{\bf M}^{(MC)}$.}
\caption{Original versus surrogate incidence matrix for the year 2018 at the HS-4 level.}
\end{adjustbox}
\end{figure}
However the sapce between single captions of the figures and the figures is still large. How can I decrease it? I tried with \setlength\parindent{0pt} but it does not work...