Taxable value (job work)

Suppose M/S.. A & Co. sent JOB WORK PURPOSE some material  to M/s Y & Co. through Job Work Challan  which Qty 40 Pcs & Taxable Value Rs. 40,000.00( excluding GST). After complet the work M/S. Y & Co. return back 40 Pcs. material through Job Work Challan in schedule time & mention taxable value (Rs. 40,000+1,200=41200) ( excluding GST) & also produce his INVOICE (LABOUR CHARGES) value Rs. 1200 + GST 18%

Now my question is taxable value is correct which Mr. Y mention in his job work challan