oops: Fix randNumber()

This addresses an issue where the `randNumber()` function would crash on
32-Bit systems if the ticket format was set to a really high amount of
digits (eg. ###################). This is because the `max()` value that
was being passed to `mt_rand()` exceeded the `mt_getrandmax()` limit which
caused an error. This updates the function to generate a random number for
each digit to avoid the `mt_getrandmax()` limit.