I think
Neeru, I think what he means is that INS gives out a fixed # of green cards per year. ( I think it is 150K or something ), which are further split into country level visa limits. And according to AC-21, these unused limits can be re-used between countries.
However, from what I have heard, thanks to the slow speed of INS, they never even finish the first level quota, not because there weren't any applications left, but because they can't process fast enough.
I don't think that would be a problem esp. that october is around.