The colored progress circles and filters displayed throughout Memorang represent your distribution of mastery scores across all content. Unlike other learning systems, these scores are not a grade. Rather, they represent the following statement:
"What is the probability that the learner has mastered this item?"
These scores are updated every time you answer a learning item, and naturally decay over time if the learning item belongs to one of your active study schedules.
The calculation is based upon a proprietary machine-learning algorithm powered by Memorang's proprietary AIBL (Artificial-Intelligence Based Learning) system. It's based upon a multitude of factors including but not limited to your speed, confidence, correctness, guessing probability, history on the item, time since last seen, difficulty level, performance on similar items, and much more.
The end result is that you can be confident that any content with "green" is something that you have truly mastered, which allows you to better focus on where you should study next.