The fourth part covers a code requirement that is also the moment when the designer takes ownership of the result: the reasoned judgement of acceptability.
What the code requires
Section 10.2.1 of NTC 2018 requires a reasoned judgement of acceptability, to demonstrate the reliability of the calculation model. It is the check that the number returned by the software makes physical sense.
Three approximate checks
Supported by simplified checks done by hand and compared with the software output: self-weight of the structure (difference below 1%), seismic mass (12%, explained by column base restraint), base shear in both directions (6.5% in X, 4.5% in Y). All acceptable.