You've got two ticks on the ballot paper. One chooses your local MP. The other largely determines how many seats your chosen party gets, if it qualifies.
I work through the room-of-chairs example, the 5% or one-electorate rule, why TOP received more than 63,000 votes but no MPs in 2023, and how ACT qualified below 5% in 2008. Then we get to the part after election nigh...