How reviews are scheduled
When a card comes back
Your rating sets the wait before the card is due again. A 1 brings it back in 2 minutes, a 2 in 10 minutes, a 3 in a day, a 4 in 3 days and a 5 in 7 days.
Every 4 or 5 in a row doubles the wait. A card you keep rating 5 comes back after 7 days, then 14, then 28, and so on, up to a year. Any rating below 4 starts the run over.
Why the gaps grow is covered in Why spaced repetition works.
Which card comes next
- Due cards first. Lower-rated cards are much more likely to come up, so a 1 gets picked far more often than a 4.
- Then new cards, in the order they sit in the deck.
- When nothing is due or new, cards ahead of their review time, weighted the same way.
The same card never comes up twice in a row unless it's the only one left.
Mastery
Mastery adds up your latest rating on every card and divides by the most you could have, which is 5 times the number of cards. A card you haven't studied counts as 0. So a deck of 10 cards that are all rated 4 is at 80%.
The bar on each deck shows how many cards sit at each rating.
Streak
Your streak counts the days in a row you've reviewed at least one card. If you studied yesterday but not yet today, it still counts. Days follow your own time zone.