You have inquired as to guidance on the R-3 Budget Exhibit.  The Financial Management Regulation (FMR) 7000.14-R contains all of the budget exhibits for RDT&E, and Procurement.  The guidance is located in Volume 2B Chapter 5 for RDT&E, Volume 2B Chapter 4 for Procurment.  Volume 2A and Volume 2B in the FMR 7000.14-R  contain information on Budget Formulation and presentation for all Appropriations.  You can locate the FMR on the Under Secretary of Defense (Comptroller) website located at <comptroller.defense.gov>.

Most Services/Agencies have various instructions on the writing of the budget exhibits so I would refer you back to your specific command direction.  I would strongly suggest you seek additional guidance from the Comptroller or lead Budget Analyst.