Starvation formula??? or bug?

[PvK]

I had thought starvation worked something like:

(Supplies Used) minus (Supplies Available) equals number of starvation effects.

Starvation effects then sprinkled randomly over non-leaders who need food, and double-hits giving disease.

I was thus very surprised when my army took a province and I took many more starvation and disease hits than I expected:

Supplies: 50 Supply Usage: 86

So I'd expect about 36 starving units, with perhaps a few diseased.

Result: 62 units starving, 16 units starving and diseased!

Looking more closely, there are about 50 non-starving units in the province... but I also have two Endless Bags of Wine, on sneaking units.

So I am wondering if I just had a wrong idea of how the formula worked, or maybe if relying on bags of wine on hidden units results in extra starvation damage when and if you don't have enough supplies, due to what would seem to be a bug (such items only counting for the starvation check, but then not for the starvation effects)?

At any rate, I'd like to know better how this works, to avoid losing my men in large numbers in future. Any information? Illwinter? Anyone?

PvK