If it can't convert and needs to show both, no worries, but shouldn't it also show weight? Kind of important in a freighter, it's the unit demand is shown in, same as pax for other planes. So max capacity = 155.6m^3/5495 cu ft/15195kg
If there's not enough room for all 3, then cargo weight is the equivalent of pax. Volume is actually irrelevant for most freighters, isn't it? Are there any that are volume limited?