Fields on schema, show undefined and int32

The fields on Schema, show as int32 and undefined. Is it because of null values in some of the documents, does the fields show as Undefined.?

If a collection contains documents in which not all fields contain a value, the missing values display as undefined . Refer to

Correct. When a document in a collection has null value for a field, in schema view, that field value is categorised/displayed as undefined type.