The Second Preference Category has two subsections. This is the "B" Category which includes: Spouses and Children, and Unmarried Sons and Daughters of Permanent
Residents: 114,200, plus the number (if any) by which the worldwide family preference level exceeds 226,000, plus any unused first preference numbers:
B. (F2B) Unmarried Sons and Daughters (21 years of age or older) of Permanent Residents: 23% of the overall second preference limitation.
The B category allots so many visas for unmarried sons and daughters over the age of 21 years of age.
What does a Beneficiary do if the visa number is current?
Again, when a visa number becomes current, that is the priority date of the visa is before the date listed on the visa bulletin for that particular category, the beneficiary can apply for a green card at a consular post and enter the United States as an immigrant or apply for adjustment of status if in the United States and still in valid legal non-immigrant status.