Total the fees for multiple exam registrations.
Exam registration totals the per-paper entry fee across every exam, then adds the surcharges that late entries attract and any centre administration charge levied once per session. Separating the penalties is the point: late fees are commonly 40 to 100 percent of the entry fee itself and are entirely avoidable, so seeing them as a line rather than folded into the total is what changes behaviour next session. Late entries are capped at the exam count so the arithmetic cannot exceed what you registered for.
Fees
Standard fees = exams x fee per exam; penalties = late entries x late surcharge
Total
Total = standard fees + penalties + centre administration fee
Usually only partly, and only before the entry deadline. After entries are submitted to the awarding body most centres refund nothing, because the fee has already been paid on your behalf.
Because they are frequently processed as late or individual entries rather than as part of a bulk cohort submission, which loses the centre's batch discount and can attract a separate administration charge.