As mentioned above it's all about the ratio. Even though the listed hitch weight is 680# I would bet that the real weight will be real close to what you're seeing now maybe even a bit heavier. The shipping weight on that unit is 7350# and 12% of that would be 882#. The GVWR is 10,850 so the TW if you ever reached that would be well over 1000#.
Salem 29RKSS Pushing a 2500 Mega-Cab CTD!
Gotta go campin!