If you know the Emp_Id's of the employees whose Emp_Acc_no need to be reverted, then you can do the following:
UPDATE Employee SET Emp_acc_no = 'CorrectAcctountNumber' WHERE Emp_id = 12345;
Since there are only eight rows, I would do them one by one carefully. Be very very careful to include the where clause, or you will destroy the account numbers of all employees!
Test it in a dev server to make sure you are doing the right thing.