The JF-17 line says "NEW". But we know there have been payments since Yr 16 and Yr 17. So the 3 fighters here are not the three from the previous 2 years. i.e. this suggests 6 fighter ordered now by Nigeria
According to the recent 2018 Nigerian Appropriation Bill, Nigeria is going to pay in instalments for the three JF-Thunder.
Original document: http://www.budgetoffice.gov.ng/index.php/2018-budget-proposal