These data are generated from the RangeMessage.xml file provided by the ISBN Agency. The distributed version matches the date in the version for this module. You can retrieve this yourself at https://www.isbn-international.org/range_file_generation. This file is included as part of the distribution and should be installed at ~lib/Business/ISBN/Data/RangeMessage.xml.
If you want to use a different RangeMessage.xml file, you can set the ISBN_RANGE_MESSAGE environment variable to the alternate location before you load Business::ISBN. This way, you can use the latest (or even earlier) data without having to install something new or wait for an update to this module.
If the default RangeMessage.xml or your alternate one is not available, the module falls back to data included in Data.pm. However, that data are likely to be older. If it does not find that file, it looks for RangeMessage.xml in the current directory.
The data are in %Business::ISBN::country_data (although the "country" part is historical). If you want to see where the data are from, check ::ISBN::country_data{_source}.