Please note what you issue is salary slip and not attendance break-up slip. All that is required is to mention attendance in number of days in the salary slip. From the number of days for which a salary is paid, it is obvious that you have included paid offs as well.
Do you have any sense of insecurity that some authority could question on the attendance on the salary slip, does it include weekly offs as well or on all the days of the month your employees worked? But then to show that the employees have given weekly off, you need to maintain attendance register properly and no need to reflect weekly offs even on salary slip as corroborative evidence.
I agree with Mr.Dinesh & there is no necessity to mention about the Weekly offs in the pay slip & related records to be maintained for the verification purpose by the Statutory authorities but in some of the companies the leave availed in that particular month & data on balance leave is being mentioned in the Pay slip for the convenience of the employee.