\documentclass{article}

\usepackage{agda}

\begin{document}

\begin{AgdaAlign}
\begin{code}%
\>[0]\AgdaKeyword{module}\AgdaSpace{}%
\AgdaModule{Issue2733-2}\AgdaSpace{}%
\AgdaKeyword{where}\<%
\end{code}

Indentation should be inserted before \AgdaKeyword{postulate}, but not
before the last occurrence of \AgdaPrimitiveType{Set}, which should be
aligned with the penultimate occurrence of \AgdaPrimitiveType{Set}:
\begin{code}%
\>[0][@{}l@{\AgdaIndent{1}}]%
\>[2]\AgdaKeyword{postulate}\<%
\\
\>[2][@{}l@{\AgdaIndent{0}}]%
\>[4]\AgdaPostulate{A}%
\>[7]\AgdaSymbol{:}\AgdaSpace{}%
\AgdaPrimitive{Set}\<%
\\
%
\>[4]\AgdaPostulate{B}%
\>[7]\AgdaSymbol{:}%
\>[3I]\AgdaPrimitive{Set}\AgdaSpace{}%
\AgdaSymbol{→}\<%
\\
\>[.][@{}l@{}]\<[3I]%
\>[9]\AgdaPrimitive{Set}\<%
\end{code}
\end{AgdaAlign}

\end{document}
