Difference between base supply and unit supply

[Kingfisher]

What is the difference between the supply level shown in the base screen from those listed on the individual unit screen?

In a current hotseat game the Japanese base in Shortlands has been isolated and pounded for several weeks, with the level of supply shown in the base screen reduced to zero.

However, when I click on the individual unit screens they show plenty of supplies on hand. In fact, of the 15 units in the hex, all but 2 have a surplus, some at 3x the min required.

[decaro]

I assume base supply includes the resources demanded by an airfield, port, etc., while unit supply doesn't take any of that infrastructure into account.

However, I have noticed that IJ forces can still resist attack w/base supply severely in the red; I know the IJA was resourceful, but perhaps it's something that should be retooled in CF.

[xj900uk]

Officially units take their own supply at the base, 'base supply' is what's left for repairs, building, restocking ships etc