Did I write my candidate number in the wrong place?

For both my EDUQAS English Language exams I wrote my centre and candidate number, but the space for the candidate number had 5 boxes instead of only 4. I’m worried that I may have missed something or I mixed it up with the centre number but that has 5 numbers so if I did it wouldn’t fit in the candidate number box. Plus I doubt I would mix them up twice. Does anyone know why there’s an extra box for the candidate number? For all my other exams it was only 4 boxes.