I've set up a number range as follows:
Z1 000000871414846215 000000871414899999
So the number contains 12 digits. De category says length - 13 digit and check digit = 1.
When I am creating a new material and enter Z1 as catgegory, a 13-digit number gets created: 871414846215 + an extra digit which I assume is the check digit.
Can someone confirm whether this is the right configuration or not?