D is the code for box 16. Part III is two columns and they are completely separate. The amount for box 12 is not provided and they are referring you to a statement. An amount should be listed.
You'll find the meaning of the codes by line number, for schedule K-1 (1120-S), on page 2 here: https://www.irs.gov/pub/irs-pdf/f1120ssk.pdf
- Box 16 code D = Distributions
- Box 12 code P = Domestic production activities information (but there is no item for P with an "*" though)