[charconv.from.chars] Clarify effect of from_chars

source/utilities.tex

@@ -15543,9 +15543,14 @@
 with remaining characters \tcode{x123}.
 \end{example}
 \end{itemize}
-In any case, the resulting \tcode{value} is one of
-at most two floating-point values
-closest to the value of the string matching the pattern.
+In any case, let $x$ be the numeric value obtained by parsing the subject sequence.
+If $x$ can be exactly represented in \placeholder{floating-point-type},
+\tcode{value} has value $x$.
+Otherwise, if $x$ is between two adjacent values
+of type \placeholder{floating-point-type},
+\tcode{value} is an implementation-defined choice of either of those values.
+Otherwise, \tcode{value} is the value closest to $x$ and representable in
+\placeholder{floating-point-type}.
 
 \pnum
 \throws