As one of the main benefits of administering option values list, Advanced Select List custom field brings you the posibility to import the values into your instance of JIRA, what might be useful, if you administer your values by another system. This can be done by importing CSV type text file.
The values you import to your custom field option list are subject to few validations, that should keep your data integrity and custom field correct usability. For example, you cannot import wrong values of Valid From and Valid To fields (Valid To > Valid From). Check chapter Imported Values Validations for details.