The French have an amusing habit when it comes to communicating numbers. It seems for one reason or another they are incapable of delivering a string of single digits in conversation. No, it has to be done in twos, in pairs.
For example, take an arbituarary eight digit number (06672582) – this is how it would translate into words:
In English: Oh double six, seven two five eight two.
In French: zero-six, sixty-seven, twenty-five, eighty-two
Voila – the French use more or less the same number of words, but do so in this irritating yet ‘easy-to-remeber’ fashion. However – the whole system falls down when they have an odd number of digits to recite.
To get around this problem some try to stick in a ‘hundred’ figure somewhere, others chose to isolate a digit at the beginning or at the end of the number, but reading out a single digit is an uncomfortable change from the norm.
To you or I it would seem to be far simpler just to read the number out, but it seems the French enjoy making things more complex than they need to be. Just try opening a bank account.