Hi,
the payload role R2 is the payload, which is handed over to the adapter of the defined outbound system of your scenario.
In case of using <b1im_multimsg> in final atom0, payload role R contains all <b1im_msg> segments whereas payload role R2 only contains one concrete <b1im_msg>, which is handed over to the B1 DI API adapter.
Best regards
Bastian