Thank you. Yes, you are right, the table shows the correct file size, and instead of using RPP I tried to import the CRW file to GraphicConverter. Indeed, GraphicConverter shows the full picture size of 3298x2472. When taking a closer look to RPP I noticed a nearly hidden option "Interp". that allows to choose among VCDMF, AHDMF and Half. The latter was default and caused the image resolution reduction which I noticed.
What's still unclear: How is it possible to store 8 million x 3 x 10 bits to a 10 megabytes file without compressing? Or are neighbour pixels not completely independent, and there is a kind of delta coding?