Fires after user’s profile completeness percentage changes when saving a field.
Fires inside an AJAX call and all output is discarded. You can set transients, send notifications, write to database etc, but you cannot modify the AJAX output.
The argument is an
array('before'⇒(int),'after'⇒(int) so you can (for example) make sure to fire your code only when the percentage goes up (or down).
This will NOT take into account admin adding/removing fields until user saves something in their profile. Profile completeness is recalculated ONLY when users modify their profiles.