"No payload or runway limits" means that THAT particular airplane (of its fleet group), in this case the 772ER and 744ER, do NOT need to reduce their capacity to make this flight, aka are capable of doing it.
The thing is that within the 77 and 74 group fleet, you have the 777-200 and the 747-400 that are unable to make the gig mainly because of their nominal range being too short, hence the warning just in case you have the 772 and the 744. Since you have the 772ER and the 744ER, there will be no problema.
Please look again at the warning. It will say that there are certain planes that are unable to do it and others that are. The ones that are listed as "No payload or runway limits" are the ones that are capable of, look to select that type of aircraft to to the route.