What is the relation between RXE, RXR and RXC RDE O11 message

As per the HL7 v2

16.7.166 RDE - Pharmacy/Treatment Encoded Order Message (Event O11) (4.A.5)

RXR appears at two place one at ORDER level(let us say outer) and other ORDER_DETAIL level(inner).
What each RXR refers to…?
will both inner and outer RXR may be present in a message ? as per the spec it looks both may be present?

How do we relate RXE, RXR and RXC that appears at outer ORDER LEVEL…
Here RXR can have 1…* cardinal while RXE and RXC is 1-1 cardinal.how to relate each segments ?

This is an HL7 v2 question. This forum is specific to FHIR. You may have better luck asking on the v2 stream on chat.fhir.org (https://chat.fhir.org/#narrow/stream/229447-V2)