Your first check-in on Dingtone will earn you one star.
If you check in for seven consecutive days and earn 7 ad credits during that period, you will earn another star (for a total of two).
If you check in for another seven consecutive days and earn 14 ad credits during that period, you will earn another star (for a total of three).
If you want to keep the stars you’ve earned, you need to check in continuously every week.