The raw marks are aligned to each band. It's the aligned marks which follow the Band 5 80-89 etc thing.
So in a particular year they might decide that a raw mark of 72 in Chemistry would just satisfy the description of a Band 5 in Chemistry. So raw 72 becomes aligned 80. They then decide that a raw mark of 83 is just enough to satisfy the Band 6 description, so raw 83 becomes aligned 90. And so on.
The raw cut-off marks for each band vary from year to year, no idea what it'd be like for Standard.