I want the displayed equations to be centered in longtable, but it seems that they are shifted to the right a bit.

[![enter image description here](https://i.stack.imgur.com/TNSKm.png)](https://i.stack.imgur.com/TNSKm.png)

Here is the code.

```
\documentclass[a4paper, 11pt, oneside]{amsart}
\usepackage{amsmath,amssymb, amsthm}
\usepackage[a4paper,width=16.5cm,top=1.5cm,bottom=2.cm]{geometry}
\usepackage{ltxtable}
\usepackage{cases}
\usepackage{lipsum}

\begin{document}

\begin{longtable}{p{0.13\textwidth} | p{0.86\textwidth-2\tabcolsep}}
\hline\hline
\bf LEFT Col. & \bf RIGHT Col.\\
\hline\hline
ABC & \lipsum[2].\\
\hline
abc & \lipsum[2]
\begin{numcases}{u(r)=}
C_1 r + C_2 \log r + C_3 \log (\log r)  \\
 C_4 \log ( \log (\log r))+ C_5 \log (\log ( \log (\log r)))
\end{numcases}
hhu
\begin{align}
C_1 r + C_2 \log r + C_3 \log (\log r)+ C_4 \log ( \log (\log r))+ C_5 \log (\log ( \log (\log r)))
\end{align}
\\
\hline\hline
\end{longtable}

\end{document}

```

Besides, it seems that the table is too big. How to fix this?