In order to spray the champagne at Rockingham, Kenseth will have to have a 186 point lead at the end of the day. If Kenseth finishes 7th (or 8th and leads a lap), then even Junior winning the race and leading the most laps won't be enough points to close the gap to 186.
So 186 point lead and they get to spray at Rockingham.
No is it anywhere between 152 and 185, then the clinch as soon as the take the green flag at Homestead since 43rd palce is worth 34 points.
Junior currently has 4600 points. If here were to win the last 2 races and lead the most laps, he would add 370 points to his total. 4970 would be the points. So as soon as Kenseth (currently at 4828) gets 4971, he is the champ. He can do that by finishing 30th in both races. He can do that by finishing 7th at Rockingham. He can do that by finishing 8th and leading a lap.
Of course the target mark changes should Junior not win and lead the most laps.
One thing for certain is that if Junior doesn't finish at least 7 palces in front of Kenseth, it is over. If they both run poorly, then it is even more palces since spread in points decreases as you go down the list.