GST debit /credit note query

As  per section 34 of  the CGST act  2017  

In first  case  Supplier Mr  X  will  issue   Credit  Note  of difference amount  

In second  case  supplier  Mr  X  issue   Debit  Note  of  difference  amount 

In  GSTR 1  supplier  will show  in Table  9B  

In GSTR 3B   supplier  will  show as - Value of Taxable supply =  Value of  Invoice  +  Debit  Note - Credit Note