https://userapps.support.sap.com/sap/support/knowledge/en/3346140
3346140 - DSO calculation in FD33 and in Tcode F.30/S_ALR_87012167 | SAP Knowledge Base Article
There are the same settings for the DSO calculation in the Credit management (Tcode OBZJ) and in the AR Information system (Tcode OBDF) but gets different...