I've found from my experience of tracking these shipments that...

I've found from my experience of tracking these shipments that most runs only have 4kt onboard depending on the total for each shipment - I know the Wunma has a carrying capacity of 5kt but if they do a 20kt shipment then they'll do 5 runs with the last run slightly longer as they've cleaned and scrapped the last bit of concentrate from the Wunma. But if they do a 10kt shipment then probably only two runs.
But I'm only estimating quantities for each shipment here so easy to be out slightly over the quarter.