Under the new system, the Chase field is expanded to 16 drivers for the 10-race Chase. The 16 drivers are chosen primarily on wins during the "regular season"; if fewer than 16 drivers win races during the regular season, the remaining field is filled on the basis of regular season points. These drivers compete against each other while racing in the standard field of 43 cars. The driver with the most points after the final 10 races is declared the champion.
The new playoff system means that drivers are eliminated from title contention as the Chase progresses. The bottom four of the top-16 drivers are eliminated from title contention after the third race (Dover) in what is called the "Challenger Round", reducing the size of the field by 25%. The bottom four winless drivers have their points reset based on the standard points system, while the remaining 12 Chase drivers' points are reset to 3,000 points. The new bottom four are eliminated after the sixth Chase race (Talladega) in the "Contender Round", reducing the size of the field another 33%. Those who continue have their points all reset to 4,000. Then the "Eliminator Round" involves axing 50% of the Chase grid, cutting the drivers 5th-8th in the points after the penultimate race at Phoenix, and the top four drivers have their point totals reset to 5,000 so that they are tied for the final race at Homestead-Miami for the title run. Of these four drivers, the driver with the best finish at Homestead is then the crowned series champion (these drivers do not earn bonus points for leading a lap or leading the most laps).
https://en.wikipedia.org/wiki/Chase_for_the_Sprint_Cup#cite_note-9 Any Chase driver who wins a race is automatically guaranteed a spot in the next round. Up to three drivers thus can advance to the next round of the Chase through race wins, regardless of their actual points position when the elimination race in that round happens. The remaining drivers advance on points.