How do purchased Supplies work?

[Dogface]

In the Camp / Army Management screen, there is a button marked "SUPPLY". How much do I need? How does it work?

If I buy 2,500 supply and go into battle I get one supply wagon with an unspecified amount of supply. If I buy 35,000 supply and go into battle I still only get one supply wagon with an unspecified amount of supply.

2,500 supply = one supply wagon 

35,000 supply = one supply wagon

[pandakraut]

You only get one wagon per corps and that wagon holds as much supply as you fill it with. So if you only have 2.5k supply the wagon will run out much faster than if you set it to 35k.