Election campaigns are exhausting, but don’t exhaust your vote. Keep numbering!
You have to number at least 1-5 or 1-7. But leaving at that means your vote might not count for the final seat.
In the ACT, the final seat usually depends on a tight race fought through preferences, chosen by the voters and not the parties. If you don’t choose further preferences and your numbers run out during allocation, your ballot paper is put aside and you wont get to have a say for that final seat.
So if you would prefer someone over someone else, make sure you give them a number. And if you really don’t want someone to win, make sure you preference the others.