As time was pressing, declarer, having drawn trumps and a long way out, claimed the small slam in Clubs. He says that he plays A♦ and also says that if the K♦ falls then there is an overtrick. On a "normal" distribution it is unlikely that the K♦ does drop but in this instance it obviously does. There is no doubt that if the hand had been played out the overtrick would have been made.
However, opposition say mistakenly that the K♦ does not fall and declarer accepts their word with the score entered without the overtrick.
At the end of the session, the hand records are examined whereupon the mistake is noticed and the opposition now agree that the K♦ does fall to be ruffed thereby making the Q♦ good. The director has not yet closed the scoring as other adjustments are being made.
The question is whether the score can now be adjusted to reflect the overtrick.