XTDir Promotions work managing entry Position, in a way that entries can be ordered by this field.
Promotions use the high-order digits and entries the low-order digits. As the digits are limited, you have to balance how many digits you apply to Promotions. For instance, 2-digit Promotions provide 99 promotions, from 01 up to 99.
If you are getting an error message, then XTDir is exhausting available Position digits. Please, reduce the number of digits assigned to Promotions.