Updates classification conceptual docs. (elastic#2222)

Author: szabosteve

docs/en/stack/ml/df-analytics/ml-dfa-classification.asciidoc

@@ -19,7 +19,7 @@ is for predicting discrete, categorical values.
 
 When you create a {classification} job, you must specify which field contains 
 the classes that you want to predict. This field is known as the _{depvar}_. It
-must contain no more than 30 classes. By default, all other
+can contain maximum 100 classes. By default, all other
 {ref}/put-dfanalytics.html#dfa-supported-fields[supported fields] are included
 in the analysis and are known as _{feature-vars}_. You can optionally include or 
 exclude fields. For more information about field selection, refer to the