Adjustment is not the same as Clearing.
Clearing is the sell-off of all the course spaces left over in August, and open to anyone without a University place.
These vacancies are widely advertised, and Unis open Clearing Hotlines to fill places.
Adjustment is only open to applicants who have higher results than they needed for their Firm choice - and they can, if they want to, phone 'higher grade' Unis to see if they can be accepted there. These 'vacancies' are not advertised, applicants just have to phone the Uni they want to approach.