OLL 6
Square · 4 of 9 top stickers yellow
r U2 R' U' R U' r'7 moves · Probability 1/54 · Mirror: OLL 5 · Inverse: OLL 7

Setup: apply these moves to a solved cube to reach this case
r U R' U R U2 r'Square · 4 of 9 top stickers yellow
r U2 R' U' R U' r'7 moves · Probability 1/54 · Mirror: OLL 5 · Inverse: OLL 7

r U R' U R U2 r'