\documentclass{article}
\begin{document}
\begin{table}
\small
\centering
\begin{tabular}{c|cc}
Source & Variation up (Stat. up) \% & Variation down (Stat. down) \% \\ \hline 
MatrixElement-Top2L\_SR2L & -1000.0 & 1000.0 \\ 
PartonShower-Top2L\_SR2L & 18.2554 & -18.2554 \\ 
MatrixElement-Top2L\_tW2L\_CRtt & 8.3168 & -8.3168 \\ 
PartonShower-Top2L\_tW2L\_CRtt & 15.5394 & -15.5394 \\ 
MatrixElement-Top2L\_tW2L\_VRtt & 9.2104 & -9.2104 \\ 
PartonShower-Top2L\_tW2L\_VRtt & 15.4092 & -15.4092 \\ 
FSR-Top2L\_SR2L & 6.6008 & 2.2838 \\ 
ISR-Top2L\_SR2L & 18.9319 & -21.7728 \\ 
FSR-Top2L\_tW2L\_CRtt & 0.6287 & -2.2402 \\ 
ISR-Top2L\_tW2L\_CRtt & 12.674 & -12.626 \\ 
FSR-Top2L\_tW2L\_CRttZ & -1000.0 & 1000.0 \\ 
ISR-Top2L\_tW2L\_CRttZ & -1000.0 & 1000.0 \\ 
FSR-Top2L\_tW2L\_CRWZ & -1000.0 & 1000.0 \\ 
ISR-Top2L\_tW2L\_CRWZ & -1000.0 & 1000.0 \\ 
FSR-Top2L\_tW2L\_VRtt & 2.2359 & -1.2163 \\ 
ISR-Top2L\_tW2L\_VRtt & 11.0927 & -9.9943 \\ 
\end{tabular}
\end{table}
\end{document}
