A wise agent foresees consequences before deciding; so God knew what creatures would do before decreeing
Again, it is the mark of a wise person, before deciding anything, to form in his mind an idea of what will follow from the things he is to decide and do. Since God decreed all things with perfect wisdom, he must have known, prior in the order of reason to decreeing to create this or that creature, to set such things before it, and to concur with it in this or that way, what would follow from all of it.
He must have known what the creature would freely do or leave undone once all this was in place. That knowledge is precisely the conditional knowledge in question.
Latin
XVII. Praeterea sapientis est priusquam aliquid decernat, animo conceptum habere quid secuturum sit ex rebus a se decernendis, atque faciendis. Cum ergo Deus sapientissime omnia decreverit, necesse ut ratione prius quam decreverit hunc, aut illum creare, taliaque illi objicere, & hoc, vel illo modo cum eo concurrere, nosset quid esset ex istis omnibus consecuturum, & quid, iis positis, creatura libere factura, vel omissura esset, qua in cognitione consistit scientia conditionata, de qua quaestio est.