2. The Department hereby specifies 30 per cent. as the percentage of the net annual value of a hereditament for the purposes of paragraph 4(2) of Schedule 7 to the Rates (Northern Ireland) Order 1977 (rateable net annual value of an industrial hereditament which is distinguished in the NAV list as being used wholly for industrial purposes to be nil or such percentage of its net annual value as the Department may by order specify).