Wrote down wrong question number???

So I just came back from sitting my A level maths exam and basically I had answered question 5 in the booklet. As I got to the end of the exam I was rushed and went to go and ask question 4 again on continuation paper and I have just realised that I wrote down 5 instead of 4!!! The two questions are very distinct - will they just accept that I made a dumb mistake or am I going to be punished for this somehow???

Are they doing maths A level now?
Each quation is, I believe marked by a different examiner, so they would go by the number. Isnt accuracy the key to maths? When is the next resits?

I live in New Zealand so we do all the external examinations now. I'm just not sure as to whether they will punish me based on a clearly dull mistake with writing the wrong question number down.