From memory, the NSW upper house optional preferential instructions are that you must mark at least 15 boxes. It's a balancing act between enough numbers to en

From memory, the NSW upper house optional preferential instructions are that you must mark at least 15 boxes. It's a balancing act between enough numbers to ensure that most ballots continue to count, but small enough to reduce the effort, and consequent informal votes due to errors, of voting below the line.