From: Santa Rosa, CA
The limits on stockpiling only apply after the production has been completed and resources and population used up. There are no limits during the turn itself, so you may see many more population and resources in an area than the "end of turn" cap. Also, the computer tries to move resources and popuation around automatically in order not to lose them due to stockpiling limits. So German, with 11 total population in it's areas, should be able to end the production phase with 11 poplulation as long as the areas are all linked with each other so the stored population can be moved around. Anything over 11 should be lost. The limits discussed in section 9.5 of the manual are all end of turn limits only.
In reviewing this, I did see one small discrepency in the rules and that is that a region with one factory and no resource centers can stored 1 resource at the end of the turn (as stated), but if the area has 2 or more factories, it will be able to store 2 resources. Again, during the turn up until after the point where the units are actually produced, there are no limits.
Another example is if you have 3 resource centers in an area, you can end your turn with only 3 resources remaining in the area after production. Assuming you have 3 remaining, on the next turn you will have 6 (3 plus a new 3), although some of these may be automatically moved to other areas by the computer. If these aren't used, or able to be moved to another area by the computer, the excess will be lost and you will be back to 3 when your turn is ended.
Section 9.7 details free trade and gifts. Free trade comes from Neutral (white) countries. Gifts are either the US gift to Japan or the Soviet gift to Germany (done automatically as described in the manual).