How are cases auto-numbered?
The current case auto-numbering format is "Case- 1", "Case- 2", "Case- 3". and so on. If Add Applicant is used on a case, the created case number will be the principal's case number followed by "-##". For example, if you Add Applicant to Case- 1, the created case number will be Case- 1 -01. If you add another applicant, it'll be Case- 1 -02.
Also, in the Cases page, the dependent case will be displayed with "(Dependent)" following the case number.
More on case numbering here: Can I change the auto-numbering format of cases?