In TBDY 2018 Table 3.2, Seismic Design Category is determined according to the short period design spectral acceleration coefficient SDS and Building Risk Category for DD-2 earthquake level.
Since the short period design spectral acceleration coefficient is SDS=0.565 and BRC=3 at the DD-2 earthquake level for the building, it is determined as DTS=2
When the analysis settings wizard is used, Seismic Design Category selection is automatically given according to the SDS and BRC determined in the previous steps.
Sections that cannot be selected in the Analysis Settings Wizard as per TBDY 2018 are automatically closed by the program, as shown by the shaded region in the image above.