Some of the officials might have not given any option for pay fixation. For these employees, Salary as per 6th CPC should be drawn, till option is received or upto three months from the date of notification of orders.
Accountant Pay Bill module is changed as per 7th CPC scales. There is NO special procedure or menu to Draw Salary as per 6th CPC in Pay Bill Module.
Do not change their Basic Pay. Allowances are the same as per 6th CPC. Only you have to correct their Dearness Allowance as per old rates.
Correct their salary in Pay Bill using menu Pay Bill == Correct menu.
Remember to follow the same procedure, till option is received.