Solution : https://service.sap.com/sap/support/notes/26002 (SAP Service marketplace login required)
Summary : 
      This SAP Note addresses issues with Customer Enhancement 1 (user exit) in results analysis, also referred to as 'Work in process calculation'. It highlights the absence of documentation and clarifies the functions and incorporation methods of Customer Enhancement 1, available since Release 2.2B with further enhancements in subsequent releases. Users can add to the standard selection, reflecting minor method deviations, or introduce entirely new methods through the enhancement. Steps include using Transaction CMOD for inclusion, assigning enhancement KKAG0001, and maintaining code in the Include module ZXKAGU01.
Key words : 
analysis accountingcoep_kokrs                      controlling areacoep_bukrs                      company codeaufk_aufnr                      order numberprps_pspnr                      internal project line item numberprps_posid                      work breakdown structure elementvbuk_vbeln                      sales, field       domain        meaningabgty       abgr_abgty     results analysis formawkus       abgr_awkus    transaction creation/usage/balancezlnid       zeilen_id      line idabgrverkg                  change, field       domain        meaningabgty       abgr_abgty     results analysis formawkus       abgr_awkus    transaction creation/usage/balancezlnid       zeilen_id      line idabgrkumkg                  accumulated, field       domain        meaningzlnid       zeilen_id      line idbewkz       abgr_bewkz    valuation indicatorkateg       kategorie      categoryistkumkg                  accumulated actual, sd documentobjektnummer                    cost element itemization numberbasis_planmenge                planned quantitybasis_istmenge                  actual quantitytable parameters, import parametersabgrenzungs_schluessel          results analysis keyabgrenzungs_version            results analysis versionsteuerung_kundenerweiterung_1   control cust, vbup_posnr                      line item, prerequisites missing documentation solution description, final results analysis setting, results analysis data determined
Related Notes : 
       
| 1148514 | Results analysis returns incorrect periodic values | 
| 982449 | Revenue Affecting Net Income displayed is wrong | 
| 501915 | Creation, cancellation, and usage of reserves | 
| 398627 | INFO: CO-PC-OBJ (Results analysis/WIP calculation) | 
| 208160 | Fixed portion should generally be equal zero | 
| 205671 | Results analysis customer enhancement 1: currencies | 
| 141587 | Input quantities in customer enhancement 1 | 
| 38070 | Revenue in excess of billings/revenue surplus per line ID |