When reading a super long document or textbook, Recall will generate like 400 questions for me to answer in a row. When I get some questions wrong, I won't see them again until 300+ questions later. Having the ability to set how many questions you want to master and practice at a time would significantly help break up the total studying into manageable chunks and help with information understanding and retention. Quizlet and knowt have these features and they are fantastic.