If there were 600kg's with 4 POB, a Caravan even with full tanks will be close enough to gross for any difference either way to be negligable.
I understand that the stuff was all weighed before loading, so it would appear that the required calculation was done.
For the sake of correctness, jet engines make thrust, propellor engines make power. Thats why turboprops are rated in SHP and not pounds of thrust. The lack of depth of knowledge shown by the proud instructor in this tread is startling. I truely hope you are lying about this qualification, if not its criminal that someone signed the form. Perhaps less time on pprune and more time reading books would be in order.