The Green Card Lottery cut off numbers on the DOS Visa Bulletin are effectively the upper limits for how many visas will be granted to a particular region.
The 50,000 visas available through the Green Card Lottery program are given to qualified winners of the lottery and those numbers are further distributed evenly among continents and countries. No one country receives more than 7% of the total number of visas assigned.
An applicant first becomes aware of their right to apply for a visa through this program in the spring following their application period. They then have approximately one year to apply for and receive that visa.
Typically, the name for a particular lottery is the letters “DV” followed by four numbers. The four numbers are the year in which the visa cut off occurs.
The registration period and the cut off are two years apart. The upcoming cut off is for DV-2013, so that means that applicants who registered for the Green Card Lottery in 2011 cannot apply for or receive a visa after September 30, 2013 [According to the August 2013 Department of State Visa Bulletin].
Within the Visa Bulletin, in parts B and C, are tables which represent which regions have already met their cut off.
To read the table in part B simply find the continent in which your country of origin resides and look at the second column. If there is a number there you still have time to apply for a visa. If that column says “CURRENT” there will be no more visas granted to that area for this Diversity Visa year.
The third column lists countries that have already met their 7% total limitation.
Keep in mind that at the end of September 2013, you will no longer be able to apply for a visa through DV-2013.