You are looking at the chapter on signs of predestination, not the mystery of the number of the elect, that's where you went wrong. If you look at the context it's obvious what the quote is talking about, so please don't get snarky and rude about reading comprehension

The common opinion of the Fathers and ancient theologians is without doubt that those who are saved do not represent the greater number. We may cite in favor of this view the following saints: Basil, John Chrysostom, Gregory Nazianzen, Hilary, Ambrose, Jerome, Augustine, Leo the Great, Bernard, Thomas Aquinas. Then, nearer to our own times: Molina, St. Robert Bellarmine, Suarez, Vasquez, Lessius, and St. Alphonsus. But they give this view as opinion, not as revealed truth, not as certain conclusion.

In the last century the contrary opinion, namely, of the greater number of the elect, was defended by Father Faber in England, by Monsignor Bougaud in France, by Father Castelein, S.J., in Belgium.

To conclude: some insist on the mercy of God, others on the justice of God. Neither one side nor the other gives us certitude. And the reasons of appropriateness which each invokes differ very much from the reasons of appropriateness invoked in favor of a dogma which is already certain by revelation, whereas here we are treating of a truth that is not certain.