Drivers, and racers in particular, are fanatical about their numbers. Either they've purchased magnetic numbers or they have them, literally, painted on the side of their car. No matter the reason, we have drivers call us all the time telling us they simply can't register because their number is not available.
We listened and we built a sophisticated permanent number management system that guarantees, beyond a shadow of a doubt, that a driver will have their number and their number only reserved for them.
And then they told us: "But sometimes I don't want to use that number, you know, because... "
And after that, we sort of stopped listening because drivers (amongst whom I consider myself one) are often an inane bunch. But, we did act! We recently added a new checkbox to the number pool configuration screen that allows drivers to pick either their reserved number or any other available (i.e., non-reserved) number.
We hope drivers find this logic unassailable and motor off happily into the sunset!