Today's featured site is Role-playing Games and the card is shown as follows:
RPG clearly has unanswered questions.
What is meant by the '100% answered'?
That means that (rounded towards the nearest whole number) 100% of the non-closed questions have an upvoted or accepted answer. The figure is the same as displayed on the list of all sites.
According to this answer by a former Stack Exchange developer, the number is coming from the
/stats API call which returns 134, exactly the number of questions with no upvoted or accepted answers right now.