dbms_parallel_execute.create_chunks_by_rowid not creating the correct # of chunks

Oracle 12C

I cannot get the create_chunks_by_rowid to create the correct number of chunks.

This has never worked the way I thought it would on large tables.  So I started testing using a smaller table, to see if I could find the problem.

My driver table has 20090 rows.

I want it to create 30 parallel chunks of 670 rows each.

So the chunksize is 670.

Here is the code:

1)  Create the chunks 

dbms_parallel_execute.create_chunks_by_rowid(task_name   => TaskNameIn,

                                                table_owner => 'VHOS',

                                                table_name  => 'CALENDAR_DAYS',

                                                by_row => TRUE,

                                                chunk_size  => 670);

At this point I only see 19 chunks (select * from user_parallel_execute_chunks