Here's the reply in another thread I received...
Basically, if your darts are three or more, they carry over but you don't get three more free darts each day.
If you have less than 3 darts left, you lose them but get your 3 free darts next day.
This does not seem fair to me. Everyone should get the 3 free everyday and any number of leftover darts should be added to the next free. That's the only fair way.
I'm gonna skip this game because it is designed to only make money by gem sales. You can't win with 3 darts period.