What does “within half a decade” mean in the context below? Context: the author’s dad had been an authoritative man his whole life who’s indifferent to family business, but a deadly accident crippled and mellowed him out and he can’t walk or talk much right now. “Within a few weeks, my father-who years earlier had not been able to guess my age **within half a decade**-knew about my classes, my friends, my summer job. I hadn’t told him any of it, but he’d listened to the chatter between me and Audrey.” I know that half a decade means five years, but i dont get what the sentence as a whole means. Is it 1)the dad didnt know her age exactly, so his guess was +/-5 years from her real age 2)he was so not interested in her that it would’ve taken him about 5 years(figuratively) to correctly guess her age, or is it sth else? Thanks in advance.