Hold one party’s proportional entitlement fixed at six seats. What changes when it wins more electorates?
4 electorate + 2 list = 6 MPs.
List seats fill the remaining places in the entitlement.
8 electorate + 0 list = 8 MPs.
All electorate winners keep their seats. The two excess seats enlarge Parliament; other parties keep their allocations.
Each square represents one MP. Illustrative numbers; proportional entitlement is held constant. The highlighted squares mark the number of excess seats, not particular electorates.