Rounak, 

Fee waiver conditions for NITs and IIEST SHIBPUR is as follows 

100% Tuition Fee waiver for SC/ST/PH students.

Full remission of the Tuition Fee for General and OBC students whose family income is less than Rs.1 lakh per annum.

Remission of 2/3rd of the Tuition Fee for General and OBC students whose family income is between Rs.1 lakh to Rs.5 lakh per annum.

So yes you will get remission of 2/3rd of the tuition fees only. 

Hope it helps