After each repetition, SuperMemo requests the learner to produce a grade that is supposed to reflect the accuracy of the just provided response.
The grade point scale is defined as follows:
Null (0), complete blackout; you do not even recall ever knowing the answer
Bad (1), wrong response; the correct answer seems to be familiar
Fail (2), wrong response that makes you angrily say "I knew it!"
Pass (3), answer recalled with difficulty; perhaps, slightly incorrect
Good (4), correct response provided after some hesitation
Bright (5), excellent response
Note, that in SuperMemo you are unlikely to need grades Null (0) or Bad (1).
Having responded to the question, you can specify a grade by choosing one of the three actions:
* click the corresponding grade button below the item field in the Learn window
* choose Grade from the Learn window's menu, and pick the relevant grade
* press the corresponding numeric key
You have to input a grade before you proceed with repetition. If, upon displaying the answer of an item, you choose any action different from the aforementioned, your request will be ignored and you will hear a beep (the only valid alternative is to quit the Learn window).