I mean, just to be silly, if we translate it to typical US grade scale… that’s like on the B to B- cusp which seems reasonable for the show.
The formulation is a way to collapse precise scores into a binary classification of thumbsup or thumbsdown. So, another way to put it would be 83% of reviewers 'liked it'
Side note, I used to really like Rotten Tomatoes 10+ years ago but I noticed a drop in quality, likely Goodhart's law in action as some other commenters here have pointed out.