What the runoff is doing.
Each voter ranks every option. Voting power sits with the current first remaining choice. If nobody has a majority, last place is eliminated and that power moves with the ballot.
The threshold is half of continuing power, not the original total. If a ballot has nowhere left to go, that power is exhausted and drops out of the denominator. Ties for last place break toward the option listed later on the proposal—deterministic, so a seed replays the same race.
This is a demonstration, not a claim that instant runoff is the right mechanism for every decision. Some calls need delegation, some need consent, some should not be votes at all. See the practice note on decision systems.