Iris - Marks down the racers whose place will be the same or better than their odds suggest
Masdevallia - Marks down the racers who will perform poorly (possibly the last two places)
Nazuna - Predicts randomly.

Since Iris marked only x30 (assuming I'm not lost in translation again), it means this racer is the only one to take the same or higher place than the odds say. Since x10 is not marked by her, it means that racer will not be 1st, making x30 the most probable winner.
Masdevallia marked x50 and x100, so these racers will probably be last if her mechanic really points that out.
I don't know what to do with Nazuna's predictions from now on, since there's probably no rule to them anymore.

RESULTS: x30, x20, x10, x50, x100

Everything seems to be as predicted.
x30 in first as Iris said, x50 and x100 in last as Masdevallia said.
Nazuna did predict the winner, but I can't see her other marks following any rules right now.