Each figure for maximum capacity should be assessed in accordance with Chapter 16 of the Green Guide ("the Green Guide figure") subject to the following qualifications:- (a) in arriving at "the Green Guide figure", proper and realistic allowance must be made for all factors which should reduce the permissible density in accordance with the range of maximum figures specified in paragraphs 221 and 222 of the Green Guide; (b) after assessing "the Green Guide figure", a deduction of 15% should be made to improve the safety margin.