Want to know the criteria to get an NC OBC certificate

Hello Sir/Madam , My Father is retired employee in BSNL department as TTA which is a "group C" government job( as per grade mentioned in south telecom bsnl website) and my mother is government aided school teacher with "group C" job (mentioned in salary slip). My father's pension is around 19700 per month and my mothers income is around 48888 per month, but their combined salary income is approximately 8.20 lac per annum(income criteria limit is 8 lac per annum). I have recieved a NC OBC certificate based on above details considering the fact that for government employees Class is considered not the salary income. Please tell me if what i have assumed is correct and whether I am eligible for NC OBC reservations at central educational institutions.