[spec] Fix alignment immediate in text format

document/core/exec/instructions.rst

@@ -372,6 +372,14 @@ Variable Instructions
 Memory Instructions
 ~~~~~~~~~~~~~~~~~~~
 
+.. note::
+   The alignment :math:`\memarg.\ALIGN` in load and store instructions does not affect the semantics.
+   It is an indication that the offset :math:`\X{ea}` at which the memory is accessed is intended to satisfy the property :math:`\X{ea} \mod 2^{\memarg.\ALIGN} = 0`.
+   A WebAssembly implementation can use this hint to optimize for the intended use.
+   Unaligned access violating that property is still allowed and must succeed regardless of the annotation.
+   However, it may be substantially slower on some hardware.
+
+
 .. _exec-load:
 .. _exec-loadn:
 
@@ -447,11 +455,6 @@ Memory Instructions
      (\otherwise) \\
    \end{array}
 
-.. note::
-   The alignment :math:`\memarg.\ALIGN` does not affect the semantics.
-   Unaligned access is supported for all types, and succeeds regardless of the annotation.
-   The only purpose of the annotation is to provide optimizatons hints.
-
 
 .. _exec-store:
 .. _exec-storen:

document/core/text/instructions.rst

@@ -179,7 +179,7 @@ Lexically, an |Toffset| or |Talign| phrase is considered a single :ref:`keyword
 .. math::
    \begin{array}{llclll}
    \production{memory argument} & \Tmemarg_N &::=&
-     o{:}\Toffset~~a{:}\Talign_N &\Rightarrow& \{ \ALIGN~a,~\OFFSET~o \} \\
+     o{:}\Toffset~~a{:}\Talign_N &\Rightarrow& \{ \ALIGN~n,~\OFFSET~o \} & (\iff a = 2^n) \\
    \production{memory offset} & \Toffset &::=&
      \text{offset{=}}o{:}\Tu32 &\Rightarrow& o \\ &&|&
      \epsilon &\Rightarrow& 0 \\