You can't have been paying very much attention then. These are the figures from KO.
Northcote: 470 new state houses - 300 existing state houses to be removed = 170 net gain in state houses
Mt Roskill: 4,400 new state houses - 2,732 existing state houses to be removed = 1,668 net gain in state houses
Porirua: 2,300 new state houses - 2,000 existing state houses to be removed = 300 net gain in state houses
Mangere: 5,000 new state houses - 2,700 existing state houses to be removed = 2,300 net gain in state houses
Tamaki: 3,500 new state houses - 2,800 existing state houses to be removed = 700 net gain in state houses
Oranga: 440 new state houses - 400 existing state houses to be removed = 40 net gain in state houses
For the first major developments for the Piritahi Alliance over the next 25 years, it will provide a total of 16,110 new state houses - 10,932 existing state houses to be removed = 5,178 net gain in state houses.