NBANDS determines the actual number of bands in the calculation. Mind: There is no possibility to set the number of bands during run-time in VASP.3.X. (In VASP.4.X NBANDS is as a matter of fact set on runtime, and NBANDS can be read from the INCAR file if the default should be overwritte, see Sec. 7.2). To get additional information how to set NBANDS please read also section 10.1.