"Given our sample of 200 exemplars from a universe of 9159 biological species": the comparison is to the list of 9159 spp from which they drew the sample they analyzed, which is their ref. #10:
Wood DS, Schnell GD. 1986. Revised world inventory of avian skeletal specimens. American Ornithologists Union and Oklahoma Biological Survey, Norman, Oklahoma.
There's a pdf [
here], if anyone wants it.