Dear Mr Ravindra,
The criteria of Pensionable salary is:-
Average monthly pay of the contributory period of service in the span of 60 months preceding the date of exit from the membership of the Employees' Pension Fund.
The reivsed salary of Rs. 15000/- implemented wef 01st Sep 2014. Hence prior to 31st Jul 2019 we have to calculate the pensionable salary on pro rata basis. However, after 31st Aug 2019 (being completion of 60 months continous service @ Rs. 15000/pm) we can consider Rs. 15000/-.
For example if any person retired on 31st May 2017 (being current period), the pensionable salary (prior to leaving the job) will be calculated on pro rata basis (27 months @ 6500 and 33 months (from Sep 14 to May 17)@ 15000). (27*6500+33*15000)/60 = 11175/-.
Since during the previous 60 months employee whole salary is not 15000/-, hence the average salary is coming 11175/-.
Hope I am cleared to your point.
Mr Abbas can put more light on that.