Update overview.dd

overview.dd

@@ -1074,7 +1074,7 @@ int main()
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 )
 
-$(P NB: The expectation may be that array index x represents the number x, with `i + i + 3` seeming odd at first glance.
+$(P NB: The expectation may be that array index $(D x) represents the number x, with $(D i + i + 3) seeming odd at first glance.
 
 However, if one were to consider each index, it would mean that the first element would represent 0 + 0 + 3 = 3;
 the second element would represent 1 + 1 + 3 = 5;