Hi Juha!
I have carefully listed the name and the numbers exactly how they are recorded in the BIOS report to avoid confusion.
There is not an exact "doubling", the 1944-445 doubles as 890, not the 970 but, the other figures are spot-on. I am not able to shed more light on this. However, I know the two component engines in the DB610 are listed as the 605W and 605X. It would be interesting to know how the DB610 production was accounted. I expect that the 605 component engines would have had separate identities (werke-nummer) but, the DB610-as a completed unit- would surely have also had its own werke-nummer. Sorry I don't have better information on this.
Best wishes
SM