Only the contestant whose result is closer to the target number scores points: 10 for reaching it exactly, 7 for being 1–5 away, 5 for being 6–10 away. Contestants score no points for being more than 10 away, if their calculations are flawed, or if they take too long to give a solution after saying they have not written it down. Both score if they reach the same result, or if their results are the same distance away. Should neither contestant reach the target exactly, the assistant is called upon to attempt a solution, either immediately or at a later time during the episode. In some games, there are many ways to reach the target exactly—the example target above could also be reached by 7 × (75 + 50 + 2 – 8 – 3) = 812. Not all games are solvable, and for a few selections it is impossible even to get within 10, most commonly when a contestant picks six small numbers and the target number is quite large. There is a tactical element in selecting how many large numbers to include. One large and five small numbers is the most popular selection, despite two large numbers giving the best chance of the game being solvable exactly. Selections with zero or four large numbers are generally considered the hardest. The 24 tiles are laid out in four rows, the topmost of which contains only the four large numbers. The contestant may specify how many tiles to draw from each row, or simply state how many large and small numbers will be used; in the latter case, the assistant draws the tiles randomly. The numbers are usually placed on the board from right to left, starting with the small ones, but have occasionally been displayed in scrambled order. On rare occasions, the contestant has declined to make any choices, in which case the assistant selects the tiles. Unlike the letters round, the pool of tiles is fully replenished after each numbers round. A special edition, broadcast on 15 March 2010, for two previous series champions, Kirk Bevins and Chris Davies, used instead of the usual four large numbers, the numbers 12, 37 and two numbers unrevealed for the duration of the show. In a further special broadcast on 16 August 2010 between the Series 59 finalists Charlie Reams and Junaid Mubeen, the other two numbers were revealed to be 62 and 87. The final round of the game is the "Countdown Conundrum", in which the contestants are shown a combination of two or three words with a total of nine letters. They have 30 seconds to form a single word using all the letters, and must buzz in to respond (a bell for the champion, a buzzer for the challenger).