Data for the returned review statistic.
For a resource, this is the last time that particular resource was updated.
A unique number identifying the review statistic.
The kind of object returned.
The URL of the requested resource.
OptionalcodeA resource will never have a code property.
OptionalerrorA resource will never have an error property.
Review statistics summarize the activity recorded in reviews. They contain sum the number of correct and incorrect answers for both meaning and reading. They track current and maximum streaks of correct answers. They store the overall percentage of correct answers versus total answers.
A review statistic is created when the user has done their first review on the related subject.
See
https://docs.api.wanikani.com/20170710/#review-statistics