\usepackage{booktabs} %preamble
\usepackage{multirow} %preamble
\renewcommand{\multirowsetup}{\centering}
\begin{tabular}{cccc}
\toprule
Case & Box A & Box B & Remarks \\
\midrule
\multirow{2}{10mm}{A}
& $+X$ & $-1.0$ & \multirow{2}{10mm}{B} \\
\cmidrule(lr){2-3}
& $-X$ & $-7.9$ & \\
\bottomrule
\end{tabular}