Food Supply and the Enormous Cauldron of Broth

[Come_Get_Some]

I'm presently playing a SP game and I have a small army consisting of:

7 human leaders
25 hypaspists
9 elephants

Assuming 3 units of food required for the elephants and 1 for the humans (is that correct?) the food requirements for this force should be 59. With the Enormous Cauldron of Broth my supply requirements should then be 9. In a province with a supply production of 6 I should only be short about 3 units of food, right? That would leave one elephant or three human-sized units to starve.

The supply usage listed for my army in that province is 27, and many of my units are starving. There's something I obviously don't get about supply. Can anyone illustrate what I might be doing wrong?

Barry

[Turin]

elephans are size 6, so they need 5 food each. Click on the hp of a unit to check it´s size.

[Agrajag]

Supply requirment is (Size-1) Supply per unit, with a minimum of 1.
Supply items such as the Cauldron of Broth don't add supplies, but rather reduce supply usage.
Need Not Eat units are obviously exempt from using supplies.
That's all about supplies that I can think of right now.