F is the fraction by which each transferable (un-truncated) ballot
has its value multiplied before being transferred. Each ballot that
lists a next choice.
t is the combined vote value of that candidaate's transferable ballots.
It's the combined vote value that's the important thing, rather than
the number of transferable ballots.
More justification of F = min (s/t, 1):
The voters who want to transfer from that elected candidate
should be able to transfer all their extra vote value. No one
can disagree with that. They should be able to transfer all of
their vote value that's left over from electing the candidate.
Though the truncating voter owns his own vote, he doesn't own
the right to transfer from a candidate from whom he doesn't
choose to transfer. That right goes to the voters who want to