Those are hop addition times. 20 down to 10 minutes or so for flavor, 5 minutes to 0 for aroma. I do late extract additions at flame out, as the wort is still boiling hot. And pasteurization happening in seconds at 160F is plenty to add the extract, cover & steep a few minutes while you get the ice bath ready. You do not need to boil the snot out of extracts to pasteurize them. Pasteurization happens well below boiling temp of 212F.