Although I think that it is generally a pro's number. From "the rules"
If you draw race number 13, turn it upside down. Paradoxically, the same mind that holds such control over the body is also woefully fragile and prone to superstitious thought. It fills easily with doubt and is distracted by ancillary details. This is why the tape must always be perfect, the machine silent, the kit spotless. And, if you draw the unlucky Number 13,
turn it upside down to counter-act its negative energy.