避免仍在使用的节点内存中的单词

Question

我正在使用lualatex一个文件wasp.ltx并得到

 427 words of node memory still in use:
   4 hlist, 1 vlist, 1 rule, 4 glue, 3 kern, 1 glyph, 7 attribute, 46 glue_spec
, 5 attribute_list, 1 write nodes

这里发生了什么事？我该如何避免node memory still in use？

以下是代码

\documentclass[12pt, letterpaper]{letter}

\title{First document}
\author{Randy}
\date{September 2022}

\signature{Randy}

\address{300 North Broadway \\
Lexington, KY 40508 USA}

\begin{document}

\begin{letter}{Mayor, Deputy Mayor, and Councillors; Zabbar}

  \opening{Dear Members of the Zabbar Local Council}

  Body

  \closing{Yours Sincerely,}
  \signature{Randy}

\end{letter}

\end{document}