Services
The President (for the UPSC/Joint Commission) or Governor (for a State Commission) may make regulations determining the number of Commission members and their service conditions, and the Commission's staff numbers/service conditions - though a member's own service conditions cannot be worsened after their appointment.
This gives the President/Governor authority to set the practical administrative details of how a Public Service Commission is staffed and run, while specifically protecting sitting members from having their own terms changed to their disadvantage mid-appointment.
This is why detailed regulations govern a Public Service Commission's staffing and internal administration, distinct from the constitutional protections given to the Commission's actual members.