Count diners by service
If 240 residents take dinner on Monday and fruit is included once that day, the starting requirement is 240 pieces. If 60 day students join lunch, add them only if lunch includes fruit. Keep event guests on a separate order.
Choose a unit the mess can check
For bananas served whole, ask for an approximate piece count and size band. For melon cut by the kitchen, order by weight using a trial yield. For prepared cups, ask for portion weight, delivery window and the agreed handover conditions.
Adjust for the academic calendar
Record holiday departures, exams and sports days against the next delivery. Review how many portions were served and how much usable stock remains before increasing the standing order.