Obc Ncl of children of PSU. What are my options ?

Query: Sir my father is clerk (class-3) employee in L.i.c which is PSU.His gross income is more than 6 lacs Now i got my obc ncl certificate in august 2016. By the fact he is class 3 employee. It is still valid. His taxable income from last 4 financial year. 2016-2017 10 lacs 15-16- 7 lacs 14-15 -6.15 lacs 13-14- 5 lacs Now since if in the income from last 3 fy any 1 year has less than 6 lac.. i come under non creamy layer... i just wanna ask that.. the obc ncl certificate issued on august 2016 is based on the which of the financial years 1. 2013-2014, 2014-2015,2015-2016 2. 2014-15, 2015-16,2016-17 I have the ITR for last 5 years.. also please consider that i am asking about the certificate made in 2016 august