When you have earned a sufficient number of points, you will pass a checkpoint and receive the Coffer with your reward. To claim it, tap the checkpoint icon. Join the Trading Guild and you will be able to receive more rewards for completing Quests.

When you pass a checkpoint and claim the Coffer, points will continue to accumulate. However, when the last checkpoint has been passed, you will stop earning points. Wait for the list of tasks to be updated and the scale to be reset to zero.