Why some bands gone after atmosphere correction using Sen2Cor?

Hi. I just found that after atmosphere correction, I have only band 2-7, 8A , 11 and 12. And the other three files without band identification: ‘S2A_USER_AOT_L2A_TL_SGS__20160916T153615_A006454_T33UUU_20m’, ‘S2A_USER_VIS_L2A_TL_SGS__20160916T153615_A006454_T33UUU_20m’ and ‘S2A_USER_WVP_L2A_TL_SGS__20160916T153615_A006454_T33UUU_20m’.

But band 8, for example, disappers. I have almost no idea what happened during atmosphere correction…Is it normal?

If I like to use band 8 and band4 in NDVI calculation, could I just use 8A?

Thanks. : )