Proportional Representation - How we count the Vote

Introduction
In all elections there will be a method of voting, and a method of counting the votes.
The voting method for most elections conducted in Australia is the Preferential Voting System where the voter numbers preferences for candidates.
Full preferential voting, the system used for South Australian House of Assembly parliamentary elections, requires an elector to indicate a preference for every candidate using sequential numbers (1, 2, 3, 4…)
Optional preferential requires one preference to be indicated for the candidate most preferred by the elector, and if they choose, they may give further preferences to other candidates.
Partial preferential is the voting method referred to where preferences must be indicated for at least the number of candidates to be elected. In this method, the elector may also indicate further preferences.
There are two methods of counting votes used under the preferential system.
Exclusion (Bottoms Up) is used in elections to elect one person and requires a candidate to receive an absolute majority (50% + 1) of the formal votes to be elected.
The Proportional Representation method of counting votes is used in elections to elect more than one person and requires candidates to achieve a ‘quota’ or proportion of the cotes to be elected.
This video looks specifically at proportional representation method of counting votes.