Hello hulabula.

You're actually applying the filter through the query, so instead of pulling all data from pcs_posts, you're pulling only the CONCAT function, where post_type = 'project' and post_status='publish'.

There are probably 527 more rows that are being filtered out because of the WHERE clause.

Maybe you can try creating a MySQL VIEW in PHPMyAdmin, using the same query, like this:

CREATE VIEW view1 AS SELECT
CONCAT............
FROM pcs_posts AS posts_projects
WHERE 1=1
AND posts_project.post_type = 'project'
AND posts_project.post_statys = 'publish'

Then you can create a table in wpDataTables like:

SELECT * FROM view1

And it will display only those 4 results.

Best regards.