What do the small boxes in the top right corner of the passport application mean?

What does the boxes R, D, O, and DP shown at the top right corner of page 1 mean? Also, what is required for End# and Exp# within the same box?

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The small box in the top right corner of passport application DS-11 is not to be filled in by the applicant but by the acceptance agent at the location where you submit the form.

*This can be either a passport application acceptance facility (most frequently located in post offices) or a regional passport agency.