I am not sure if I have understood your question correctly. If you mean to ask "what info is passed in the piggybacked NAS pdu?" then the below answer may help you.
As part of dedicated bearer establishment, MME sends the E-RAB setup request to the enodeB & piggybacks a NAS pdu inside this msg. This NAS pdu is nothing but the "activate dedicated EPS bearer context request'.
It contains the EPS bearer Id, Linked EPS bearer Id, QOS info, Traffic Flow Template (TFT), etc.
This info is passed to the UE while RRC Reconfiguration. In response to this NAS msg, the UE sends an activate dedicated EPS bearer context accept message to acknowledge the activation of a dedicated EPS bearer context associated with the same PDN address and APN as an already active EPS bearer context.
After receiving the response from the UE, the MME knows that the dedicated bearer establishment procedure was successful.
Hope this helps!