The actual text, it seems:
https://docs.moodle.org/26/en/Upload_users#Fields_that_can_be_included
For custom profile fields that are a menu, use the corresponding value (new in Moodle 2.3 onwards).
Example: A custom field 'Department' with one of three values 'HR', 'Marketing' or 'Training'. Just insert one of those three words (e.g. 'Training') as the value for that field.
Anyway, take a look at the following tracker entries:
https://tracker.moodle.org/browse/MDL-31654
https://tracker.moodle.org/browse/MDL-16764