Ann: Venture Books First Shipment - Riley Iron Ore Mine, page-924

Sounds normal for iron ore, actually, (especially since they had plenty more coming directly from the mine), because:

a) it's been wet weather, and a higher moisture content can cause a load to shift unexpectedly because finer particles can rise to the top faster, (and risk sinking the ship in rough waves), so it's the crew who determines the final total weight they take on, not Venture Minerals.

b) travelling north to tropical (much warmer) waters requires a few less tonnes for buoyancy differences, as explained in my earlier post about codes on the hull.

c) the nature of Iron ore (with various "gravel" sized grains and/or dust particles) can change how it settles in cargo holds after a few hours of wave motions, even if it's very dry

And in any case, a general "bulker" cargo ship like that (which is not specifically designed for Iron Ore or coal) needs to pile the load more centrally, and leave extra weight for taking on extra sea water ballast into their tanks after leaving the leave port.. (much more ballast than for lighter loads, such as woodchip or fertiliser.

So 1000 tonnes one way or the other is no big deal for Iron Ore imo

But DYOR.

GLA.