What does this message from DOS Visa Bulletin mean?

[Bengalita 12]

I was looking on the Department of State website, looking at the priority dates, and I have been wondering FOR THE LONGEST TIME...what does this message mean?

For September, F2A numbers EXEMPT from per-country limit are available to applicants from all countries with priority dates earlier than 22SEP08. F2A numbers SUBJECT to per-country limit are available to applicants chargeable to all countries EXCEPT MEXICO with priority dates beginning 22SEP08 and earlier than 01DEC08. (All F2A numbers provided for MEXICO are exempt from the per-country limit; there are no F2A numbers for MEXICO subject to per-country limit.)

Edited November 2, 2011 by zonryza

[JimVaPhuong 4,863]

Dunno. That statement has always confused me, as well. I always presumed it had something to do with the fact that Mexico always seems to be pretty much the only country that's oversubscribed in the F2A category.