Категория F2A, а F21 – это USCIS class code. Это то что у вас в гринкарте (и на въездной иммиграционной визе) будет стоять.
Вот коды для Family-based иммигрантов (кроме IR/CR):
F11 Unmarried child of U.S. citizen.
F12 Child of non-citizen classified F11.
F16 Unmarried son/daughter of U.S. citizen, adjustment.
F17 Child of F11 and F16.
F21 Spouse of LPR.
F22 Child of LPR.
F23 Child of F21 or F22.
F24 Unmarried child of LPR.
F26 Spouse of LPR, adjustment.
F27 Child of LPR, adjustment.
F31 Married child of U.S. citizen.
F32 Spouse of F31.
F33 Child of F31.
F36 Married son/daughter of U.S. citizen, adjustment.
F37 Spouse of married son/daughter of U.S. citizen, Adjustment.
F41 Brother/sister of U.S. citizen, new arrival.
F42 Spouse of F41.
F43 Child of F41.
F46 Brother/sister of U.S. citizen, adjustment.