I just reserved RTW flights using the oneworld tool (first flight is BA). It gave me a reservation number like 123XYZ.

However, when I go to manage my booking I see also another number. I click it and it shows the same itinerary. Except that my seat selections are different.

What is the extra number for?
Also, I think the reservation is now a "TA booking". Are there any issues because of that? I haven't paid the ticket yet so I could cancel and call BA if needed.