Reword and improve example

docs/diagnostics/5001.md

@@ -32,7 +32,7 @@ val f = filter
 (** + undefined value: `filter` *)
 ```
 
-Confusingly, come functions like `map` are defined both in `List` and also aliased the top level.
+Confusingly, some functions like `map` are defined both in `List` and also aliased the top level.
 
 ```sml
 val m1 = List.map
@@ -65,20 +65,22 @@ val y : x = 5
 
 ### Check signature ascription
 
-The name may be explicitly not permitted to be accessed outside of a structure due to a signature ascription.
-
-Ascribing a structure to a more restrictive signature prohibits accessing the "extra" items inside the structure.
+If the name is defined inside a structure, but the structure ascribes to a signature, and the signature does not include that name, then the name will not be available outside of the structure.
 
 ```sml
 signature SIG = sig
-  val foo : int
+  val inSigAndStruct : int
 end
 
 structure Str : SIG = struct
-  val foo = 3
-  val bar = "hi"
+  val notInSig = "hi"
+  val inSigAndStruct = String.size notInSig
 end
 
-val s = Str.bar
-(**     ^^^^^^^ undefined value: `bar` *)
+(* this is fine *)
+val n = Str.inSigAndStruct
+
+(* this is not *)
+val s = Str.notInSig
+(**     ^^^^^^^^^^^^ undefined value: `notInSig` *)
 ```