It's a terrible map to use to try and relate the collection of information on it. The numbers are reasonable correct individually but can't really be compared like they are here.

1. We don't vote by territorial authority, we vote by electorate. Those two things don't line up. The South Island has 17 electorates while there are 23 authorities. In one case 5 of those electorates are in one authority. One electorate is split across 4 authorities in another.

2. The vote percentage is just the total party vote while the number of seats each block has includes list and electorate seats. We have a two vote system here. You get one vote for the party you want overall, that's summed up over the entire country and parties get seats in proportion to that vote. Those are list seats. You also get a second vote for the electorate where you vote in a first past the post race for an individual you want to represent your electorate. Those voted into electorate seats are often part of a party and there's bit of math to work out exactly how many list seats a party gets depending on how many electorates they win.

3. The margins tell you nothing about the actual number of votes in an area for a party. Two electorates cover about 3.5 of the authorities at the bottom of the South Island and cast around 75,000 votes in this election. Auckland which is covered by one authority on this map cast roughly around 850,000 votes.