What is the criteria for OBC(NCL) for government grade C employees

My dad is a central railway govt. employee and is Grade-C employee. His income for last 3 financial year is more than 8 lacs and we dont have any extra source income.But as I have read the NCBC criteria, laid down for non-creamy eligibility,I find myself eligible for non-creamy as criteria of NCBC has asked to check the grade of govt. employees.But here tahsildar of my town says am not eligible for non-creamy certif. as income citeria doesnt permit. So,I want to know is my view of non-creamy correct and do I am eligible for non-creamy? And if am eligible and as tahsildar doesnt accept,what further steps should I take?