\begin{table}
\centering
\begin{tblr}[         %% tabularray outer open
]                     %% tabularray outer close
{                     %% tabularray inner open
colspec={Q[]},
hline{2}={1}{solid, black, 0.05em},
hline{1}={1}{solid, black, 0.1em},
hline{6}={1}{solid, black, 0.1em},
column{1}={si={table-format=-6.5,table-align-text-before=false,table-align-text-after=false,input-symbols={-,\*+()}},},
cell{1}{1}={guard,halign=c,},
}                     %% tabularray inner close
pi \\
314.15927 \\
3141.5927 \\
31415.927 \\
314159.27 \\
\end{tblr}
\end{table} 
