All bouts are rated with 0 to 5 stars.
Men
5 stars = both opponents have 331 ratings points at least ~ best 100 boxers
4 stars = both opponents have 188 ratings points at least ~ best 300 boxers
3 stars = both opponents have 83 ratings points at least ~ best 900 boxers
2 stars = both opponents have 24 ratings points at least ~ best 2700 boxers
1 stars = both opponents have 1 rating point at least = rated boxers
0 stars = one opponents has not even 1 rating point at least = not rated boxers
So the 4 star Froch-Kessler is an error according to their own criteria..