Each month, the Visa Office subdivides the annual preference and foreign state limitations specified by the INA into monthly allotments based on totals of documentarily qualified immigrant visa applicants reported at consular posts and CIS Offices, grouped by foreign state chargeability, preference category, and priority date. If there are sufficient numbers in a particular category to satisfy all reported documentarily qualified demand, the category is considered "Current." For example: If the monthly allocation target is 3,000 and there is only demand for 1,000 applicants, the category will be "Current”. Whenever the total of documentarily qualified applicants in a category exceeds the supply of numbers available for allotment for the particular month, the category is considered to be "oversubscribed" and a visa availability cut-off date is established. The cut-off date is the priority date of the first documentarily qualified applicant who could not be accommodated for a visa number. For example: If the monthly target is 3,000 and there is demand for 8,000 applicants, then it would be necessary to establish a cut-off date so that only 3,000 numbers would be allocated. In this case, the cut-off would be the priority date of the 3,001st applicant.
The link below shows the estimated total number of visas available for each employment preference category and country for fiscal year 2014.