The Limit per time slot fields only appear once Time Slot Interval is set to something other than Any — with Any selected, Sprwt skips the slot-limit check entirely, so the fields stay hidden and whatever is in them is ignored.

Be careful once you do set an interval. On a Pickup Location, leaving Max meals per time slot or Max orders per time slot blank saves it as 0, and 0 is enforced as the actual cap — that blocks every order in that slot, it does not mean unlimited. On a Delivery Route, leaving the field blank is saved as blank and the limit check is skipped for that route, which does behave as no limit. To avoid accidentally blocking pickup orders, either keep Time Slot Interval on Any or enter a real number once you turn a limit on.