If the store enables Catering Max Meals Per Time Slot and/or Catering Max Orders Per Time Slot (set on the dedicated Catering Settings screen, not the general Client Config), checking out at a given event time is blocked once that many meals (or that many separate catering orders) already fall within the configured interval around that time — e.g. "The maximum of 200 meals for this time slot has already been reached. Your current total is... Please select a different time slot or reduce your order." There's also a separate, older Catering Limit ("we can only serve N orders at the same time") that checks for overlapping event windows within an hours-before/after buffer.