In "I, Borg," while working on the invasive program designed to destroy the Borg, Geordi tells Captain Picard that within a few months the entire Borg Collective should be wiped out. How could he possibly know this? The Federation couldn't have any knowledge of the size of the Borg at this point. And even if they did, how could they possibly know how quickly the program would take to work? Geordi is smart, but I don't recall him owning a crystal ball.
What is the canon answer to this?