Clarify filter apply callable documentation with value explanation

Author: kevinzwhuang

README.md

@@ -656,9 +656,14 @@ apply that filter. The callable is passed the `records`, which is an `ActiveReco
 
 This example shows how you can implement different approaches for different filters.
 
+Note: When a filter is not supplied a `verify` callable to modify the `value` that the `apply callable recieves,
+`value` defaults to an array of the string values provided to the filter parameter.
+
 ```ruby
+# When given the following parameter:'filter[visibility]': 'public'
+
 filter :visibility, apply: ->(records, value, _options) {
-  records.where('users.publicly_visible = ?', value == :public)
+  records.where('users.publicly_visible = ?', value[0] == 'public')
 }
 ```