If this is an FEC 500,you might want to go down on the FEC forums,or the pros only.
I believe the number used to loosely mean the total max weight,with considerations for shape of items,etc.
Call sales and John will talk over the loads with you.
Fast Eddy would ordinarily pick up the question,but he is probably traveling to the Lakeland,Fl cookoff this week.
They do not monitor these forums.