左右边距不相等

Question

请查看我的 MWE。我期望奇数边距和偶数边距相同，但事实并非如此。我做错了什么？我尝试了所有建议的解决方案，但都没有用。

\documentclass[11pt,twoside,A4, english]{amsart}
\usepackage[T1]{fontenc}
\usepackage{calc}
\setlength{\footskip}{\paperheight
  -(1in+\voffset+\topmargin+\headheight+\headsep+\textheight)
  -0.75in}

\pagestyle{plain} 
%Arial
\usepackage{arial}                           % load package which provides the font
\renewcommand{\sfdefault}{ua1}               % set default serif font as Arial
\renewcommand{\familydefault}{\sfdefault}             % set default serif font as Arial
%margin
\usepackage[a4paper]{geometry}
\textwidth 17.5cm
\textheight 27cm
\evensidemargin \oddsidemargin

\setlength\topmargin{(\paperheight-\textheight
-\headheight-\headsep-\footskip)/2 - 1in}

\usepackage{fontspec}
\usepackage{polyglossia}
\usepackage{ebgaramond}
\setdefaultlanguage{italian}

\usepackage{showframe}
\begin{document}
\sloppy
%%%%%%%%%%%%%%%%%%%%%%%%%STARTHERE%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\layout



\end{document}