ORIGINAL: Ric Carpenter
When you open up Singapore under supply is another area with 2 arrows press on the left to decrease supply and the right to increase
Note well that when the "supply spinner" (it's been called that here for years even though it clicks and doesn't spin) is adjusted, the base will seek to draw 3x that number to itself if it can. So, if you want to be able to restock airplanes for example, and need a minimum of 20,000 supply, setting the spinner to 7000 will cause it to try to get 21,000. If you set it at 20,000, then 60,000. This is a number that will likely corrupt local supply flows and may very well result in supply spoilage at the recieving base.
Extensive work on base supply and supply flows was done in patches after the manual was written. The manual also does not mention stockpiling switches; they were added in patches. They are extremely important in actual gameplay, however.