Normally, in a flashcard app, you would write down a question and an answer. So you can review the question, and see if you can answer it or not. He wrote this down all as a oneliner for each of his "learnings". Its nice to see a frequency graph to see how often you are learning, but it doesn't really serve a purpose besides showing how inconsistent you are learning new things.
I would highly suggest anyone interested in the authors approach to learning to read these 2 articles about spaced-repetition-learning and flashcards, which goes into much more detail.
Not all things benefit equally from writing things down learned / flashcards. Some things can only be learned through practice, such as learning a sport you aren't familiar with such as football. But flashcards can be beneficial here to learn about the rules of football, the mechanics, terminology, etc.
The hardest part is differentiating what pieces of information benefit from using flashcards and which don't, and consistently recognizing when new information is learned / making a flashcard for it
- For 9000 cards+, reviews 100 cards a day in 20 minutes
- Delete 1 or 2 % of cards that are poorly made
- Reading a science paper is 0 to 5 questions unless to understand it well its 20 to 40.
- Enter cards through desktop app, review on mobile (this i do already)
- If memorizing saves 5 minutes in future, put it down
I only have a few hundred cards or so, I only add a handful of cards a week at best.