If the number of passengers added in $$Legs Info$$ > $$Pax$$ exceeds the aircraft capacity, which can be input in $$OPS$$ > $$Fleet Edit$$, Leon will display a warning: “Number of passengers has exceeded the capacity of the aircraft” (see example below).
The capacity of the aircraft is added in Fleet Edit screen.
The number of passengers has exceeded the capacity of the aircraft - Leon displays the exclamation mark Unknown Attachment and if you hover the mouse over it, the information will appear.