Issue #3310083: Default value for record_number_field is record_number, not record_num

src/Plugin/migrate/source/CSV.php

@@ -30,7 +30,7 @@ use League\Csv\Reader;
  * - create_record_number: (optional) Boolean value specifying whether to create
  *   an incremented value for each record in the file. Defaults to FALSE.
  * - record_number_field: (optional) The name of a field that holds an
- *   incremented value for each record in the file. Defaults to record_num.
+ *   incremented value for each record in the file. Defaults to record_number.
  *
  * @codingStandardsIgnoreStart
  *