The multi-winner RCV page of "How it Works" provides a basic understanding of how votes are counted and how multiple candidates are elected at once using ranked choice voting. The reality is that while this page gives a good overview, the counting procedure is a little more complicated, and can be done in a few different ways. This page gives a more in-depth explanation of how votes are tabulated in Cambridge, Massachusetts.
In 1939, the City of Cambridge adopted a city charter in which nine City Councilors and six School Committee members are elected at-large using ranked choice voting. With Cambridge’s system, a candidate must win a certain proportion of the votes in order to be elected. This winning fraction of the votes is referred to as the threshold, or "quota," for election.
DETERMINING THE THRESHOLD
The threshold is determined by dividing the total number of valid ballots cast by the number of positions to be elected plus one and then adding one to the resulting dividend.
Thus, to elect 9 City Councilors, the total number of valid ballots cast is divided by 10; to elect 6 School Committee members, the total is divided by 7. And in both cases, 1 is added to the result of the division.
For example, if 25,000 valid ballots are cast for City Council, the threshold will be 2,501 (25,000 divided by 10, plus 1).
COUNTING THE BALLOTS
The count begins by sorting ballots by the first choice, or Number 1 choice, selected on each valid ballot. This is generally known as the "First Count."
Any candidates who reach the necessary threshold with Number 1 choices are declared elected. Any extra votes they receive beyond the threshold (surplus votes) are redistributed to the candidates marked next in preference (the Number 2 choice) on those excess ballots. (See Transferring the Surplus below.)
The count continues with the elimination of those candidates receiving fewer than fifty votes in the first count. Their ballots are then counted for the other candidates according to the next marked choice.
[To understand how ballots are marked, see "How to Mark a Ballot"]
After each distribution, the candidate now having the lowest number of votes is eliminated and his/her ballots counted for the next indicated choice (Number 2, 3, 4, etc.)
As candidates reach the threshold through the addition of redistributed ballots to their totals, they are declared elected and no further ballots are transferred to them.
This process continues until all candidates have been eliminated except the nine winners for City Council or the six winners for School Committee.
TRANSFERRING THE SURPLUS
The technique used by Cambridge for selecting ballots to transfer from a candidate’s surplus to bring the candidate down to threshold is called the Cincinnati Method. The method is as follows: the ballots of the candidate who has surplus votes are numbered sequentially in the order in which they have been counted (that is, in the sequence dictated by the random draw of precincts). Then, every nth ballot is drawn and transferred to a continuing candidate until the original candidate is credited with ballots equaling no more than the threshold. "n" is the nearest whole number computed by the formula:
A ballot selected by this method that does not show a preference for a continuing candidate is skipped and remains with the original candidate. If not enough ballots are removed when ballots n, 2n, 3n, . . . have been transferred, the sequence starts again with n+1, 2n+1, 3n+1, etc.
This information and more is available on Cambridge's website which explains how its municipal elections are conducted.