With 11½ points East should invite Game in NT by bidding 2NT. Opener, with 15 points, accepts the invitation and bids 3NT.

At all three tables 9 or 10 tricks were easily made. Four of the tricks were coming from the ♣ suit, East's 5-card length providing two of them !   So, at all times count your Length Points !

Only at one table, after the false suit 1♦ response, the 3NT contract was reached. The other two tables remained stuck at the part-score contract of 1NT.