Display: (Missing Resource Amount / Selected Planet's_Resourse_ProductionPerHour)
Or something along those lines.
This would allow one to easily plan when they would need to precisely get back on to upgrade, or in the case of missing more then one type of resources and you need a lot more of one type then the other; you could determine if it would be efficient to let the mines produce one and transfer over the other or transfer both.
Edit: Oops. I think this is a Commander feature, nevermind.