Error on mercure bill's number function.

We have this error on a client (dolibarr3.3.3, don't see a correction in last commits)

Sample draft bill for november :
mask = FC{yy}{mm}{000@99}
result {mm} = 11, $maskraz = 12
On validation, number -> FC131160 instead of FC131112 (because FC131101 was already use)