be precise where the default type constraint actually comes from

doc/Language/variables.pod6

@@ -843,16 +843,16 @@ unsuccessfully, resetting the answer to 42.
 
 =head1 Type Constraints and Initialization
 
-Variables can have a type constraint, which goes between the declarator and
-the variable name.
+Variables have a type constraint via the L<container|/language/containers> they
+are bound to, which goes between the declarator and the variable name. The default type constraint is L<Mu|/type/Mu>
 
     my Int $x = 42;
     $x = 'a string';
     CATCH { default { put .^name, ': ', .Str } }
     # OUTPUT: X::TypeCheck::Assignment: Type check failed in assignment to $x; expected Int but got Str ("a string")
 
 If a scalar variable has a type constraint but no initial value, it is
-initialized with the type object of the constraint type.
+initialized with the type object of the default value of the container it is bound to.
 
     my Int $x;
     say $x.^name;       # Int