Well, it just means that if you want to build up an army as efficiently as possible, you wait with building medium tanks till you researched basic medium tank.
That would be somewhere in late 1938, and you fill the entire production qeue on jan. 1936 with IC's in every province above 4 IC. By that I mean about 17-18 series of 2 factories, one series in each province over 4 IC.
However, if you want, I could PM you with some hints and tips to make the learning curve less steep for ya... since this is rather off topic isn't it? :rofl: