Having looked into this further I agree you are quite right, the number of letters in the answer should be 10. Unfortunately, one of our reference books gives 9 letters, but having since looked at various references I find the answer is 10.
Further to this, I am not after any answers but I would just like to know if anyone else has found that the answers to numbers 8 and 17 on page 11 are the same date or is it just me.