DSSSB TGT Result - Waiting list chances?

my brother applied for dsssb tgt eng. Total vacancies were around 500+ and e-dossier was submitted. The main list is out and their name is in the waiting list. Since there are multiple exams and overlapping post codes, what are the realistic chances of getting selected from during the waiting period?

Does the waiting list move much in DSSSB TGT exams? Any experience or insights would be really helpful. Thanks!