what the 10,000# means is more likely the trailer's Gross weight meaning that the weight of the empty trailer plus the cargo on the trailer can equal up to 10,000# the way to check this would be to look at the tag on the trailer next to the VIN# plate...it will state whether its a 10,000# GVWR (gross weight) or 10,000# payload...i would guess that trailer is prolly around 2000# empty so that would mean that if the tag says 10,000LBS GVWR then you could load 8,000# on it if the GVWR is more like 12,000# then you can actually load 10,000# on it all this is very confusing to start out but once you get going you will pick it up fast
one thing to keep in mind is your state's CDL requirements...add the GVWR of your trailer to the GVWR of your truck (located on the door sticker) if the two numbers together are greater than 26000# you more than likely need a Class A Commercial Driver's License...but that my friend is a whole other topic/thread in itself