1 white chip = 1 additional unit of whatever type is placed on top of it. An example would be a fighter unit on 3 white chips is 4 fighters(often written 4 ftr or 4 ftrs).
1 red chip = 5 additional units of whatever type is placed on top of it. An example would be an infantry unit on 2 red chips is 11 infantry(often written 11 inf). Heh-heh!
Unless you buy extra pieces, on eBay fer example, you will have to limit your countries that you have forces in.
You might also check out your local rag tag hobby/toy store, Goodwill or other second hand shops.