incorporate Jonny's comments

Author: mumian

articles/azure-resource-manager/bicep/data-types.md

@@ -274,7 +274,7 @@ All strings in Bicep support interpolation. To inject an expression, surround it
 var storageName = 'storage${uniqueString(resourceGroup().id)}'
 ```
 
-## Multi-line strings
+### Multi-line strings
 
 In Bicep, multi-line strings are defined between three single quote characters (`'''`) followed optionally by a newline (the opening sequence), and three single quote characters (`'''` - the closing sequence). Characters that are entered between the opening and closing sequence are read verbatim, and no escaping is necessary or possible.
 
@@ -319,7 +319,7 @@ is ${blocked}'''
 
 ## Union types
 
-In Bicep, a union type allows the creation of a combined type consisting of a set of sub-types. An assignment is valid if any of the individual sub-type assignments are permitted. The `|` character separates individual sub-types using an _or_ condition. For example, the syntax _'a' | 'b'_ means that a valid assignment could be either _'a'_ or _'b'_. Union types are translated into the allowed-value constraint in Bicep, so only literals are permitted as members. Unions can include any number of literal-typed expressions.
+In Bicep, a union type allows the creation of a combined type consisting of a set of sub-types. An assignment is valid if any of the individual sub-type assignments are permitted. The `|` character separates individual sub-types using an _or_ condition. For example, the syntax _'a' | 'b'_ means that a valid assignment could be either _'a'_ or _'b'_. Union types are translated into the [allowed-value](../templates/definitions.md#allowed-values) constraint in Bicep, so only literals are permitted as members. Unions can include any number of literal-typed expressions.
 
 ```bicep
 type color = 'Red' | 'Blue' | 'White'
@@ -372,6 +372,9 @@ There are some limitations with union type.
   type foo = 'a' | 1
   ```
 
+* Only literals are permitted as members.
+* All literals must be of the same primitive data type (e.g., all strings or all integers).
+
 The union type syntax can be used in [user-defined data types](./user-defined-data-types.md).
 
 ## Secure strings and objects