Interpretation of grades Auto and N/A in Repetition History Dialog Box

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Subject: SM17

Question:

I have an item with repetition history:

• No Rep Date Hour Grd Interval Prior Difficulty S R est. vs. R Dev Postp.
• Next 2:0 May 15, 2018 Future Future 7 18.2% 50% (50) 21 83.16% (90) 0% 5
• 4 1:0 May 08, 2018 16:47:31 Auto - 547 50% (-) 4 - - -
• 3 Reset
• 2 2:0 Feb 07, 2018 - N/A 648 - 50% (-) - -% (-) - -
• 1 1:0 Apr 29, 2016 16:30:00 4 - 427 50% (68.4) 4 - - -
• 0

What does "Auto" and "N/A" mean under the Grades column? Is not explained in documentation https://help.supermemo.org/wiki/Repetition_history

Answer:

Automatic repetition

There are some 14 contexts in which Grade=Auto may appear. Usually it means the grade was issued without a user decision:

• forced topic review
• automatic commit (e.g. as a browser operation)
• guessed from the last repetition date in element data
• guessed from missing history for topics
• converted from old grading styles in older SuperMemos
• upgrade from an out of range grade in older SuperMemos

Grade not available (N/A)

There are some 20 contexts in which Grade=N/A may appear. Most come from bug protections, defaults, errors, crashes, or incompatibilities. For example:

• unmatching conversion from older SuperMemos
• grade cannot be guessed due to missing data
• default grade data before the grade is issued (e.g. computer crash will keep it unchanged)
• errors in repetition history text file (e.g. erroneous edits by the user)
• errors in element transfer text file (e.g. erroneous edits by the user)