When studying Sentence, and using the Overall filter, I clicked on the Mastery levels, to see which sentences were at the level, but the the results seemed incorrect. For example when I clicked on Level 2, I got nothing despite the graph showing 8. On other levels only a small number of sentences appeared when many sentences were expected.
Notably, everything works as expected on different types of schedules e.g. Vocab, Grammar, Kanji, or when the individual category for "Listening" or "Structure" are selected i.e. The problem only occurs specifically for Sentences and Overall